diff --git a/chapter_array_and_linkedlist/array.md b/chapter_array_and_linkedlist/array.md index 354d64717..c8cb05a89 100755 --- a/chapter_array_and_linkedlist/array.md +++ b/chapter_array_and_linkedlist/array.md @@ -230,7 +230,7 @@ elementAddr = firtstElementAddr + elementLength * elementIndex ```zig title="array.zig" // 随机返回一个数组元素 - pub fn randomAccess(nums: []i32) i32 { + fn randomAccess(nums: []i32) i32 { // 在区间 [0, nums.len) 中随机抽取一个整数 var randomIndex = std.crypto.random.intRangeLessThan(usize, 0, nums.len); // 获取并返回随机元素 @@ -389,7 +389,7 @@ elementAddr = firtstElementAddr + elementLength * elementIndex ```zig title="array.zig" // 扩展数组长度 - pub fn extend(mem_allocator: std.mem.Allocator, nums: []i32, enlarge: usize) ![]i32 { + fn extend(mem_allocator: std.mem.Allocator, nums: []i32, enlarge: usize) ![]i32 { // 初始化一个扩展长度后的数组 var res = try mem_allocator.alloc(i32, nums.len + enlarge); std.mem.set(i32, res, 0); @@ -597,7 +597,7 @@ elementAddr = firtstElementAddr + elementLength * elementIndex ```zig title="array.zig" // 在数组的索引 index 处插入元素 num - pub fn insert(nums: []i32, num: i32, index: usize) void { + fn insert(nums: []i32, num: i32, index: usize) void { // 把索引 index 以及之后的所有元素向后移动一位 var i = nums.len - 1; while (i > index) : (i -= 1) { @@ -608,7 +608,7 @@ elementAddr = firtstElementAddr + elementLength * elementIndex } // 删除索引 index 处元素 - pub fn remove(nums: []i32, index: usize) void { + fn remove(nums: []i32, index: usize) void { // 把索引 index 之后的所有元素向前移动一位 var i = index; while (i < nums.len - 1) : (i += 1) { @@ -764,7 +764,7 @@ elementAddr = firtstElementAddr + elementLength * elementIndex ```zig title="array.zig" // 遍历数组 - pub fn traverse(nums: []i32) void { + fn traverse(nums: []i32) void { var count: i32 = 0; // 通过索引遍历数组 var i: i32 = 0; @@ -899,7 +899,7 @@ elementAddr = firtstElementAddr + elementLength * elementIndex ```zig title="array.zig" // 在数组中查找指定元素 - pub fn find(nums: []i32, target: i32) i32 { + fn find(nums: []i32, target: i32) i32 { for (nums) |num, i| { if (num == target) return @intCast(i32, i); } diff --git a/chapter_array_and_linkedlist/linked_list.md b/chapter_array_and_linkedlist/linked_list.md index 5d6dbff9a..ca3d6110b 100755 --- a/chapter_array_and_linkedlist/linked_list.md +++ b/chapter_array_and_linkedlist/linked_list.md @@ -506,14 +506,14 @@ comments: true ```zig title="linked_list.zig" // 在链表的结点 n0 之后插入结点 P - pub fn insert(n0: ?*inc.ListNode(i32), P: ?*inc.ListNode(i32)) void { + fn insert(n0: ?*inc.ListNode(i32), P: ?*inc.ListNode(i32)) void { var n1 = n0.?.next; n0.?.next = P; P.?.next = n1; } // 删除链表的结点 n0 之后的首个结点 - pub fn remove(n0: ?*inc.ListNode(i32)) void { + fn remove(n0: ?*inc.ListNode(i32)) void { if (n0.?.next == null) return; // n0 -> P -> n1 var P = n0.?.next; @@ -653,7 +653,7 @@ comments: true ```zig title="linked_list.zig" // 访问链表中索引为 index 的结点 - pub fn access(node: ?*inc.ListNode(i32), index: i32) ?*inc.ListNode(i32) { + fn access(node: ?*inc.ListNode(i32), index: i32) ?*inc.ListNode(i32) { var head = node; var i: i32 = 0; while (i < index) : (i += 1) { @@ -813,7 +813,7 @@ comments: true ```zig title="linked_list.zig" // 在链表中查找值为 target 的首个结点 - pub fn find(node: ?*inc.ListNode(i32), target: i32) i32 { + fn find(node: ?*inc.ListNode(i32), target: i32) i32 { var head = node; var index: i32 = 0; while (head != null) { diff --git a/chapter_array_and_linkedlist/list.md b/chapter_array_and_linkedlist/list.md index a2c4a4a84..37dc6d7d5 100755 --- a/chapter_array_and_linkedlist/list.md +++ b/chapter_array_and_linkedlist/list.md @@ -1552,7 +1552,7 @@ comments: true ```zig title="my_list.zig" // 列表类简易实现 - pub fn MyList(comptime T: type) type { + fn MyList(comptime T: type) type { return struct { const Self = @This(); diff --git a/chapter_computational_complexity/space_time_tradeoff.md b/chapter_computational_complexity/space_time_tradeoff.md index b88d53c30..abdf5a166 100755 --- a/chapter_computational_complexity/space_time_tradeoff.md +++ b/chapter_computational_complexity/space_time_tradeoff.md @@ -177,23 +177,22 @@ comments: true === "Zig" ```zig title="leetcode_two_sum.zig" - const SolutionBruteForce = struct { - pub fn twoSum(self: *SolutionBruteForce, nums: []i32, target: i32) [2]i32 { - _ = self; - var size: usize = nums.len; - var i: usize = 0; - // 两层循环,时间复杂度 O(n^2) - while (i < size - 1) : (i += 1) { - var j = i + 1; - while (j < size) : (j += 1) { - if (nums[i] + nums[j] == target) { - return [_]i32{@intCast(i32, i), @intCast(i32, j)}; - } + // 方法一:暴力枚举 + fn twoSumBruteForce(nums: []i32, target: i32) [2]i32 { + _ = self; + var size: usize = nums.len; + var i: usize = 0; + // 两层循环,时间复杂度 O(n^2) + while (i < size - 1) : (i += 1) { + var j = i + 1; + while (j < size) : (j += 1) { + if (nums[i] + nums[j] == target) { + return [_]i32{@intCast(i32, i), @intCast(i32, j)}; } } - return undefined; } - }; + return undefined; + } ``` ### 方法二:辅助哈希表 @@ -361,22 +360,21 @@ comments: true === "Zig" ```zig title="leetcode_two_sum.zig" - const SolutionHashMap = struct { - pub fn twoSum(self: *SolutionHashMap, nums: []i32, target: i32) ![2]i32 { - _ = self; - var size: usize = nums.len; - // 辅助哈希表,空间复杂度 O(n) - var dic = std.AutoHashMap(i32, i32).init(std.heap.page_allocator); - defer dic.deinit(); - var i: usize = 0; - // 单层循环,时间复杂度 O(n) - while (i < size) : (i += 1) { - if (dic.contains(target - nums[i])) { - return [_]i32{dic.get(target - nums[i]).?, @intCast(i32, i)}; - } - try dic.put(nums[i], @intCast(i32, i)); + // 方法二:辅助哈希表 + fn twoSumHashTable(nums: []i32, target: i32) ![2]i32 { + _ = self; + var size: usize = nums.len; + // 辅助哈希表,空间复杂度 O(n) + var dic = std.AutoHashMap(i32, i32).init(std.heap.page_allocator); + defer dic.deinit(); + var i: usize = 0; + // 单层循环,时间复杂度 O(n) + while (i < size) : (i += 1) { + if (dic.contains(target - nums[i])) { + return [_]i32{dic.get(target - nums[i]).?, @intCast(i32, i)}; } - return undefined; + try dic.put(nums[i], @intCast(i32, i)); } - }; + return undefined; + } ``` diff --git a/chapter_computational_complexity/time_complexity.md b/chapter_computational_complexity/time_complexity.md index 1e9bfaa21..44ad40fbd 100755 --- a/chapter_computational_complexity/time_complexity.md +++ b/chapter_computational_complexity/time_complexity.md @@ -1363,7 +1363,7 @@ $$ } } return count; - } + } ``` ![time_complexity_constant_linear_quadratic](time_complexity.assets/time_complexity_constant_linear_quadratic.png) @@ -1788,7 +1788,7 @@ $$ ```zig title="time_complexity.zig" // 指数阶(循环实现) - fn exponential(n: i32) i32{ + fn exponential(n: i32) i32 { var count: i32 = 0; var bas: i32 = 1; var i: i32 = 0; @@ -1802,7 +1802,7 @@ $$ } // count = 1 + 2 + 4 + 8 + .. + 2^(n-1) = 2^n - 1 return count; - } + } ``` ![time_complexity_exponential](time_complexity.assets/time_complexity_exponential.png) @@ -1909,7 +1909,7 @@ $$ ```zig title="time_complexity.zig" // 指数阶(递归实现) - fn expRecur(n: i32) i32{ + fn expRecur(n: i32) i32 { if (n == 1) return 1; return expRecur(n - 1) + expRecur(n - 1) + 1; } @@ -2054,8 +2054,7 @@ $$ ```zig title="time_complexity.zig" // 对数阶(循环实现) - fn logarithmic(n: f32) i32 - { + fn logarithmic(n: f32) i32 { var count: i32 = 0; var n_var = n; while (n_var > 1) @@ -2171,8 +2170,7 @@ $$ ```zig title="time_complexity.zig" // 对数阶(递归实现) - fn logRecur(n: f32) i32 - { + fn logRecur(n: f32) i32 { if (n <= 1) return 0; return logRecur(n / 2) + 1; } @@ -2324,8 +2322,7 @@ $$ ```zig title="time_complexity.zig" // 线性对数阶 - fn linearLogRecur(n: f32) i32 - { + fn linearLogRecur(n: f32) i32 { if (n <= 1) return 1; var count: i32 = linearLogRecur(n / 2) + linearLogRecur(n / 2); diff --git a/chapter_hashing/hash_map.md b/chapter_hashing/hash_map.md index 7d49dd6bc..00469674a 100755 --- a/chapter_hashing/hash_map.md +++ b/chapter_hashing/hash_map.md @@ -1158,7 +1158,110 @@ $$ === "Zig" ```zig title="array_hash_map.zig" + // 键值对 int->String + const Entry = struct { + key: usize = undefined, + val: []const u8 = undefined, + pub fn init(key: usize, val: []const u8) Entry { + return Entry { + .key = key, + .val = val, + }; + } + }; + + // 基于数组简易实现的哈希表 + fn ArrayHashMap(comptime T: type) type { + return struct { + bucket: ?std.ArrayList(?T) = null, + mem_allocator: std.mem.Allocator = undefined, + + const Self = @This(); + + // 构造函数 + pub fn init(self: *Self, allocator: std.mem.Allocator) !void { + self.mem_allocator = allocator; + // 初始化一个长度为 100 的桶(数组) + self.bucket = std.ArrayList(?T).init(self.mem_allocator); + var i: i32 = 0; + while (i < 100) : (i += 1) { + try self.bucket.?.append(null); + } + } + + // 析构函数 + pub fn deinit(self: *Self) void { + if (self.bucket != null) self.bucket.?.deinit(); + } + + // 哈希函数 + fn hashFunc(key: usize) usize { + var index = key % 100; + return index; + } + + // 查询操作 + pub fn get(self: *Self, key: usize) []const u8 { + var index = hashFunc(key); + var pair = self.bucket.?.items[index]; + return pair.?.val; + } + + // 添加操作 + pub fn put(self: *Self, key: usize, val: []const u8) !void { + var pair = Entry.init(key, val); + var index = hashFunc(key); + self.bucket.?.items[index] = pair; + } + + // 删除操作 + pub fn remove(self: *Self, key: usize) !void { + var index = hashFunc(key); + // 置为 null ,代表删除 + self.bucket.?.items[index] = null; + } + + // 获取所有键值对 + pub fn entrySet(self: *Self) !*std.ArrayList(T) { + var entry_set = std.ArrayList(T).init(self.mem_allocator); + for (self.bucket.?.items) |item| { + if (item == null) continue; + try entry_set.append(item.?); + } + return &entry_set; + } + + // 获取所有键 + pub fn keySet(self: *Self) !*std.ArrayList(usize) { + var key_set = std.ArrayList(usize).init(self.mem_allocator); + for (self.bucket.?.items) |item| { + if (item == null) continue; + try key_set.append(item.?.key); + } + return &key_set; + } + + // 获取所有值 + pub fn valueSet(self: *Self) !*std.ArrayList([]const u8) { + var value_set = std.ArrayList([]const u8).init(self.mem_allocator); + for (self.bucket.?.items) |item| { + if (item == null) continue; + try value_set.append(item.?.val); + } + return &value_set; + } + + // 打印哈希表 + pub fn print(self: *Self) !void { + var entry_set = try self.entrySet(); + defer entry_set.deinit(); + for (entry_set.items) |item| { + std.debug.print("{} -> {s}\n", .{item.key, item.val}); + } + } + }; + } ``` ## 6.1.4. 哈希冲突 diff --git a/chapter_heap/heap.md b/chapter_heap/heap.md index 2703adc0e..4e309bf18 100644 --- a/chapter_heap/heap.md +++ b/chapter_heap/heap.md @@ -397,7 +397,21 @@ comments: true === "Zig" ```zig title="my_heap.zig" + // 获取左子结点索引 + fn left(i: usize) usize { + return 2 * i + 1; + } + // 获取右子结点索引 + fn right(i: usize) usize { + return 2 * i + 2; + } + + // 获取父结点索引 + fn parent(i: usize) usize { + // return (i - 1) / 2; // 向下整除 + return @divFloor(i - 1, 2); + } ``` ### 访问堆顶元素 @@ -479,7 +493,10 @@ comments: true === "Zig" ```zig title="my_heap.zig" - + // 访问堆顶元素 + fn peek(self: *Self) T { + return self.maxHeap.?.items[0]; + } ``` ### 元素入堆 @@ -694,7 +711,28 @@ comments: true === "Zig" ```zig title="my_heap.zig" + // 元素入堆 + fn push(self: *Self, val: T) !void { + // 添加结点 + try self.maxHeap.?.append(val); + // 从底至顶堆化 + try self.siftUp(self.size() - 1); + } + // 从结点 i 开始,从底至顶堆化 + fn siftUp(self: *Self, i_: usize) !void { + var i = i_; + while (true) { + // 获取结点 i 的父结点 + var p = parent(i); + // 当“越过根结点”或“结点无需修复”时,结束堆化 + if (p < 0 or self.maxHeap.?.items[i] <= self.maxHeap.?.items[p]) break; + // 交换两结点 + try self.swap(i, p); + // 循环向上堆化 + i = p; + } + } ``` ### 堆顶元素出堆 @@ -998,7 +1036,38 @@ comments: true === "Zig" ```zig title="my_heap.zig" + // 元素出堆 + fn poll(self: *Self) !T { + // 判断处理 + if (self.isEmpty()) unreachable; + // 交换根结点与最右叶结点(即交换首元素与尾元素) + try self.swap(0, self.size() - 1); + // 删除结点 + var val = self.maxHeap.?.pop(); + // 从顶至底堆化 + try self.siftDown(0); + // 返回堆顶元素 + return val; + } + // 从结点 i 开始,从顶至底堆化 + fn siftDown(self: *Self, i_: usize) !void { + var i = i_; + while (true) { + // 判断结点 i, l, r 中值最大的结点,记为 ma + var l = left(i); + var r = right(i); + var ma = i; + if (l < self.size() and self.maxHeap.?.items[l] > self.maxHeap.?.items[ma]) ma = l; + if (r < self.size() and self.maxHeap.?.items[r] > self.maxHeap.?.items[ma]) ma = r; + // 若结点 i 最大或索引 l, r 越界,则无需继续堆化,跳出 + if (ma == i) break; + // 交换两结点 + try self.swap(i, ma); + // 循环向下堆化 + i = ma; + } + } ``` ### 输入数据并建堆 * @@ -1113,7 +1182,18 @@ comments: true === "Zig" ```zig title="my_heap.zig" - + // 构造函数,根据输入列表建堆 + fn init(self: *Self, allocator: std.mem.Allocator, nums: []const T) !void { + if (self.maxHeap != null) return; + self.maxHeap = std.ArrayList(T).init(allocator); + // 将列表元素原封不动添加进堆 + try self.maxHeap.?.appendSlice(nums); + // 堆化除叶结点以外的其他所有结点 + var i: usize = parent(self.size() - 1) + 1; + while (i > 0) : (i -= 1) { + try self.siftDown(i - 1); + } + } ``` 那么,第二种建堆方法的时间复杂度时多少呢?我们来做一下简单推算。 diff --git a/chapter_searching/binary_search.md b/chapter_searching/binary_search.md index a2677d520..36bcabfaa 100755 --- a/chapter_searching/binary_search.md +++ b/chapter_searching/binary_search.md @@ -237,7 +237,25 @@ $$ === "Zig" ```zig title="binary_search.zig" - + // 二分查找(双闭区间) + fn binarySearch(comptime T: type, nums: std.ArrayList(T), target: T) T { + // 初始化双闭区间 [0, n-1] ,即 i, j 分别指向数组首元素、尾元素 + var i: usize = 0; + var j: usize = nums.items.len - 1; + // 循环,当搜索区间为空时跳出(当 i > j 时为空) + while (i <= j) { + var m = (i + j) / 2; // 计算中点索引 m + if (nums.items[m] < target) { // 此情况说明 target 在区间 [m+1, j] 中 + i = m + 1; + } else if (nums.items[m] > target) { // 此情况说明 target 在区间 [i, m-1] 中 + j = m - 1; + } else { // 找到目标元素,返回其索引 + return @intCast(T, m); + } + } + // 未找到目标元素,返回 -1 + return -1; + } ``` ### “左闭右开”实现 @@ -431,7 +449,25 @@ $$ === "Zig" ```zig title="binary_search.zig" - + // 二分查找(左闭右开) + fn binarySearch1(comptime T: type, nums: std.ArrayList(T), target: T) T { + // 初始化左闭右开 [0, n) ,即 i, j 分别指向数组首元素、尾元素+1 + var i: usize = 0; + var j: usize = nums.items.len; + // 循环,当搜索区间为空时跳出(当 i = j 时为空) + while (i <= j) { + var m = (i + j) / 2; // 计算中点索引 m + if (nums.items[m] < target) { // 此情况说明 target 在区间 [m+1, j) 中 + i = m + 1; + } else if (nums.items[m] > target) { // 此情况说明 target 在区间 [i, m) 中 + j = m; + } else { // 找到目标元素,返回其索引 + return @intCast(T, m); + } + } + // 未找到目标元素,返回 -1 + return -1; + } ``` ### 两种表示对比 diff --git a/chapter_searching/hashing_search.md b/chapter_searching/hashing_search.md index 7187ee2ae..0cc61b3a4 100755 --- a/chapter_searching/hashing_search.md +++ b/chapter_searching/hashing_search.md @@ -119,7 +119,13 @@ comments: true === "Zig" ```zig title="hashing_search.zig" - + // 哈希查找(数组) + fn hashingSearchArray(comptime T: type, map: std.AutoHashMap(T, T), target: T) T { + // 哈希表的 key: 目标元素,value: 索引 + // 若哈希表中无此 key ,返回 -1 + if (map.getKey(target) == null) return -1; + return map.get(target).?; + } ``` 再比如,如果我们想要给定一个目标结点值 `target` ,获取对应的链表结点对象,那么也可以使用哈希查找实现。 @@ -230,7 +236,13 @@ comments: true === "Zig" ```zig title="hashing_search.zig" - + // 哈希查找(链表) + fn hashingSearchLinkedList(comptime T: type, map: std.AutoHashMap(T, *inc.ListNode(T)), target: T) ?*inc.ListNode(T) { + // 哈希表的 key: 目标结点值,value: 结点对象 + // 若哈希表中无此 key ,返回 null + if (map.getKey(target) == null) return null; + return map.get(target); + } ``` ## 10.3.2. 复杂度分析 diff --git a/chapter_searching/linear_search.md b/chapter_searching/linear_search.md index 0efe70c17..2b653a040 100755 --- a/chapter_searching/linear_search.md +++ b/chapter_searching/linear_search.md @@ -151,7 +151,18 @@ comments: true === "Zig" ```zig title="linear_search.zig" - + // 线性查找(数组) + fn linearSearchArray(comptime T: type, nums: std.ArrayList(T), target: T) T { + // 遍历数组 + for (nums.items) |num, i| { + // 找到目标元素, 返回其索引 + if (num == target) { + return @intCast(T, i); + } + } + // 未找到目标元素,返回 -1 + return -1; + } ``` 再比如,我们想要在给定一个目标结点值 `target` ,返回此结点对象,也可以在链表中进行线性查找。 @@ -304,7 +315,17 @@ comments: true === "Zig" ```zig title="linear_search.zig" - + // 线性查找(链表) + fn linearSearchLinkedList(comptime T: type, node: ?*inc.ListNode(T), target: T) ?*inc.ListNode(T) { + var head = node; + // 遍历链表 + while (head != null) { + // 找到目标结点,返回之 + if (head.?.val == target) return head; + head = head.?.next; + } + return null; + } ``` ## 10.1.2. 复杂度分析 diff --git a/chapter_sorting/bubble_sort.md b/chapter_sorting/bubble_sort.md index 8b2ee71c2..ff2f2ce5f 100755 --- a/chapter_sorting/bubble_sort.md +++ b/chapter_sorting/bubble_sort.md @@ -228,7 +228,23 @@ comments: true === "Zig" ```zig title="bubble_sort.zig" - + // 冒泡排序 + fn bubbleSort(nums: []i32) void { + // 外循环:待排序元素数量为 n-1, n-2, ..., 1 + var i: usize = nums.len - 1; + while (i > 0) : (i -= 1) { + var j: usize = 0; + // 内循环:冒泡操作 + while (j < i) : (j += 1) { + if (nums[j] > nums[j + 1]) { + // 交换 nums[j] 与 nums[j + 1] + var tmp = nums[j]; + nums[j] = nums[j + 1]; + nums[j + 1] = tmp; + } + } + } + } ``` ## 11.2.2. 算法特性 @@ -461,5 +477,24 @@ comments: true === "Zig" ```zig title="bubble_sort.zig" - + // 冒泡排序(标志优化) + fn bubbleSortWithFlag(nums: []i32) void { + // 外循环:待排序元素数量为 n-1, n-2, ..., 1 + var i: usize = nums.len - 1; + while (i > 0) : (i -= 1) { + var flag = false; // 初始化标志位 + var j: usize = 0; + // 内循环:冒泡操作 + while (j < i) : (j += 1) { + if (nums[j] > nums[j + 1]) { + // 交换 nums[j] 与 nums[j + 1] + var tmp = nums[j]; + nums[j] = nums[j + 1]; + nums[j + 1] = tmp; + flag = true; + } + } + if (!flag) break; // 此轮冒泡未交换任何元素,直接跳出 + } + } ``` diff --git a/chapter_sorting/insertion_sort.md b/chapter_sorting/insertion_sort.md index db96e330a..1eacaca60 100755 --- a/chapter_sorting/insertion_sort.md +++ b/chapter_sorting/insertion_sort.md @@ -197,7 +197,20 @@ comments: true === "Zig" ```zig title="insertion_sort.zig" - + // 插入排序 + fn insertionSort(nums: []i32) void { + // 外循环:base = nums[1], nums[2], ..., nums[n-1] + var i: usize = 1; + while (i < nums.len) : (i += 1) { + var base = nums[i]; + var j: usize = i; + // 内循环:将 base 插入到左边的正确位置 + while (j >= 1 and nums[j - 1] > base) : (j -= 1) { + nums[j] = nums[j - 1]; // 1. 将 nums[j] 向右移动一位 + } + nums[j] = base; // 2. 将 base 赋值到正确位置 + } + } ``` ## 11.3.2. 算法特性 diff --git a/chapter_sorting/quick_sort.md b/chapter_sorting/quick_sort.md index 7308bd5d1..376d12dfb 100755 --- a/chapter_sorting/quick_sort.md +++ b/chapter_sorting/quick_sort.md @@ -262,7 +262,26 @@ comments: true === "Zig" ```zig title="quick_sort.zig" + // 元素交换 + fn swap(nums: []i32, i: usize, j: usize) void { + var tmp = nums[i]; + nums[i] = nums[j]; + nums[j] = tmp; + } + // 哨兵划分 + fn partition(nums: []i32, left: usize, right: usize) usize { + // 以 nums[left] 作为基准数 + var i = left; + var j = right; + while (i < j) { + while (i < j and nums[j] >= nums[left]) j -= 1; // 从右向左找首个小于基准数的元素 + while (i < j and nums[i] <= nums[left]) i += 1; // 从左向右找首个大于基准数的元素 + swap(nums, i, j); // 交换这两个元素 + } + swap(nums, i, left); // 将基准数交换至两子数组的分界线 + return i; // 返回基准数的索引 + } ``` !!! note "快速排序的分治思想" @@ -420,7 +439,16 @@ comments: true === "Zig" ```zig title="quick_sort.zig" - + // 快速排序 + fn quickSort(nums: []i32, left: usize, right: usize) void { + // 子数组长度为 1 时终止递归 + if (left >= right) return; + // 哨兵划分 + var pivot = partition(nums, left, right); + // 递归左子数组、右子数组 + quickSort(nums, left, pivot - 1); + quickSort(nums, pivot + 1, right); + } ``` ## 11.4.2. 算法特性 @@ -734,7 +762,36 @@ comments: true === "Zig" ```zig title="quick_sort.zig" + // 选取三个元素的中位数 + fn medianThree(nums: []i32, left: usize, mid: usize, right: usize) usize { + // 使用了异或操作来简化代码 + // 异或规则为 0 ^ 0 = 1 ^ 1 = 0, 0 ^ 1 = 1 ^ 0 = 1 + if ((nums[left] < nums[mid]) != (nums[left] < nums[right])) { + return left; + } else if ((nums[mid] < nums[left]) != (nums[mid] < nums[right])) { + return mid; + } else { + return right; + } + } + // 哨兵划分(三数取中值) + fn partition(nums: []i32, left: usize, right: usize) usize { + // 选取三个候选元素的中位数 + var med = medianThree(nums, left, (left + right) / 2, right); + // 将中位数交换至数组最左端 + swap(nums, left, med); + // 以 nums[left] 作为基准数 + var i = left; + var j = right; + while (i < j) { + while (i < j and nums[j] >= nums[left]) j -= 1; // 从右向左找首个小于基准数的元素 + while (i < j and nums[i] <= nums[left]) i += 1; // 从左向右找首个大于基准数的元素 + swap(nums, i, j); // 交换这两个元素 + } + swap(nums, i, left); // 将基准数交换至两子数组的分界线 + return i; // 返回基准数的索引 + } ``` ## 11.4.5. 尾递归优化 @@ -924,5 +981,22 @@ comments: true === "Zig" ```zig title="quick_sort.zig" - + // 快速排序(尾递归优化) + fn quickSort(nums: []i32, left_: usize, right_: usize) void { + var left = left_; + var right = right_; + // 子数组长度为 1 时终止递归 + while (left < right) { + // 哨兵划分操作 + var pivot = partition(nums, left, right); + // 对两个子数组中较短的那个执行快排 + if (pivot - left < right - pivot) { + quickSort(nums, left, pivot - 1); // 递归排序左子数组 + left = pivot + 1; // 剩余待排序区间为 [pivot + 1, right] + } else { + quickSort(nums, pivot + 1, right); // 递归排序右子数组 + right = pivot - 1; // 剩余待排序区间为 [left, pivot - 1] + } + } + } ``` diff --git a/chapter_stack_and_queue/queue.md b/chapter_stack_and_queue/queue.md index faadf95ba..88b54aab7 100755 --- a/chapter_stack_and_queue/queue.md +++ b/chapter_stack_and_queue/queue.md @@ -842,7 +842,90 @@ comments: true === "Zig" ```zig title="linkedlist_queue.zig" + // 基于链表实现的队列 + fn LinkedListQueue(comptime T: type) type { + return struct { + const Self = @This(); + front: ?*inc.ListNode(T) = null, // 头结点 front + rear: ?*inc.ListNode(T) = null, // 尾结点 rear + queSize: usize = 0, // 队列的长度 + mem_arena: ?std.heap.ArenaAllocator = null, + mem_allocator: std.mem.Allocator = undefined, // 内存分配器 + + // 构造函数(分配内存+初始化队列) + pub fn init(self: *Self, allocator: std.mem.Allocator) !void { + if (self.mem_arena == null) { + self.mem_arena = std.heap.ArenaAllocator.init(allocator); + self.mem_allocator = self.mem_arena.?.allocator(); + } + self.front = null; + self.rear = null; + self.queSize = 0; + } + + // 析构函数(释放内存) + pub fn deinit(self: *Self) void { + if (self.mem_arena == null) return; + self.mem_arena.?.deinit(); + } + + // 获取队列的长度 + pub fn size(self: *Self) usize { + return self.queSize; + } + + // 判断队列是否为空 + pub fn isEmpty(self: *Self) bool { + return self.size() == 0; + } + + // 访问队首元素 + pub fn peek(self: *Self) T { + if (self.size() == 0) @panic("队列为空"); + return self.front.?.val; + } + + // 入队 + pub fn push(self: *Self, num: T) !void { + // 尾结点后添加 num + var node = try self.mem_allocator.create(inc.ListNode(T)); + node.init(num); + // 如果队列为空,则令头、尾结点都指向该结点 + if (self.front == null) { + self.front = node; + self.rear = node; + // 如果队列不为空,则将该结点添加到尾结点后 + } else { + self.rear.?.next = node; + self.rear = node; + } + self.queSize += 1; + } + + // 出队 + pub fn poll(self: *Self) T { + var num = self.peek(); + // 删除头结点 + self.front = self.front.?.next; + self.queSize -= 1; + return num; + } + + // 将链表转换为数组 + pub fn toArray(self: *Self) ![]T { + var node = self.front; + var res = try self.mem_allocator.alloc(T, self.size()); + std.mem.set(T, res, @as(T, 0)); + var i: usize = 0; + while (i < res.len) : (i += 1) { + res[i] = node.?.val; + node = node.?.next; + } + return res; + } + }; + } ``` ### 基于数组的实现 @@ -1445,7 +1528,93 @@ comments: true === "Zig" ```zig title="array_queue.zig" + // 基于环形数组实现的队列 + fn ArrayQueue(comptime T: type) type { + return struct { + const Self = @This(); + nums: []T = undefined, // 用于存储队列元素的数组 + cap: usize = 0, // 队列容量 + front: usize = 0, // 队首指针,指向队首元素 + queSize: usize = 0, // 尾指针,指向队尾 + 1 + mem_arena: ?std.heap.ArenaAllocator = null, + mem_allocator: std.mem.Allocator = undefined, // 内存分配器 + + // 构造函数(分配内存+初始化数组) + pub fn init(self: *Self, allocator: std.mem.Allocator, cap: usize) !void { + if (self.mem_arena == null) { + self.mem_arena = std.heap.ArenaAllocator.init(allocator); + self.mem_allocator = self.mem_arena.?.allocator(); + } + self.cap = cap; + self.nums = try self.mem_allocator.alloc(T, self.cap); + std.mem.set(T, self.nums, @as(T, 0)); + } + + // 析构函数(释放内存) + pub fn deinit(self: *Self) void { + if (self.mem_arena == null) return; + self.mem_arena.?.deinit(); + } + + // 获取队列的容量 + pub fn capacity(self: *Self) usize { + return self.cap; + } + + // 获取队列的长度 + pub fn size(self: *Self) usize { + return self.queSize; + } + + // 判断队列是否为空 + pub fn isEmpty(self: *Self) bool { + return self.queSize == 0; + } + + // 入队 + pub fn push(self: *Self, num: T) !void { + if (self.size() == self.capacity()) { + std.debug.print("队列已满\n", .{}); + return; + } + // 计算尾指针,指向队尾索引 + 1 + // 通过取余操作,实现 rear 越过数组尾部后回到头部 + var rear = (self.front + self.queSize) % self.capacity(); + // 尾结点后添加 num + self.nums[rear] = num; + self.queSize += 1; + } + + // 出队 + pub fn poll(self: *Self) T { + var num = self.peek(); + // 队首指针向后移动一位,若越过尾部则返回到数组头部 + self.front = (self.front + 1) % self.capacity(); + self.queSize -= 1; + return num; + } + + // 访问队首元素 + pub fn peek(self: *Self) T { + if (self.isEmpty()) @panic("队列为空"); + return self.nums[self.front]; + } + + // 返回数组 + pub fn toArray(self: *Self) ![]T { + // 仅转换有效长度范围内的列表元素 + var res = try self.mem_allocator.alloc(T, self.size()); + std.mem.set(T, res, @as(T, 0)); + var i: usize = 0; + var j: usize = self.front; + while (i < self.size()) : ({ i += 1; j += 1; }) { + res[i] = self.nums[j % self.capacity()]; + } + return res; + } + }; + } ``` 以上代码仍存在局限性,即长度不可变。然而,我们可以通过将数组替换为列表(即动态数组)来引入扩容机制,有兴趣的同学可以尝试实现。 diff --git a/chapter_stack_and_queue/stack.md b/chapter_stack_and_queue/stack.md index cf0dbf376..8e81edb39 100755 --- a/chapter_stack_and_queue/stack.md +++ b/chapter_stack_and_queue/stack.md @@ -771,7 +771,79 @@ comments: true === "Zig" ```zig title="linkedlist_stack.zig" + // 基于链表实现的栈 + fn LinkedListStack(comptime T: type) type { + return struct { + const Self = @This(); + stackTop: ?*inc.ListNode(T) = null, // 将头结点作为栈顶 + stkSize: usize = 0, // 栈的长度 + mem_arena: ?std.heap.ArenaAllocator = null, + mem_allocator: std.mem.Allocator = undefined, // 内存分配器 + + // 构造函数(分配内存+初始化栈) + pub fn init(self: *Self, allocator: std.mem.Allocator) !void { + if (self.mem_arena == null) { + self.mem_arena = std.heap.ArenaAllocator.init(allocator); + self.mem_allocator = self.mem_arena.?.allocator(); + } + self.stackTop = null; + self.stkSize = 0; + } + + // 析构函数(释放内存) + pub fn deinit(self: *Self) void { + if (self.mem_arena == null) return; + self.mem_arena.?.deinit(); + } + + // 获取栈的长度 + pub fn size(self: *Self) usize { + return self.stkSize; + } + + // 判断栈是否为空 + pub fn isEmpty(self: *Self) bool { + return self.size() == 0; + } + + // 访问栈顶元素 + pub fn top(self: *Self) T { + if (self.size() == 0) @panic("栈为空"); + return self.stackTop.?.val; + } + + // 入栈 + pub fn push(self: *Self, num: T) !void { + var node = try self.mem_allocator.create(inc.ListNode(T)); + node.init(num); + node.next = self.stackTop; + self.stackTop = node; + self.stkSize += 1; + } + + // 出栈 + pub fn pop(self: *Self) T { + var num = self.top(); + self.stackTop = self.stackTop.?.next; + self.stkSize -= 1; + return num; + } + + // 将栈转换为数组 + pub fn toArray(self: *Self) ![]T { + var node = self.stackTop; + var res = try self.mem_allocator.alloc(T, self.size()); + std.mem.set(T, res, @as(T, 0)); + var i: usize = 0; + while (i < res.len) : (i += 1) { + res[res.len - i - 1] = node.?.val; + node = node.?.next; + } + return res; + } + }; + } ``` ### 基于数组的实现 @@ -1178,7 +1250,59 @@ comments: true === "Zig" ```zig title="array_stack.zig" + // 基于数组实现的栈 + fn ArrayStack(comptime T: type) type { + return struct { + const Self = @This(); + stack: ?std.ArrayList(T) = null, + + // 构造函数(分配内存+初始化栈) + pub fn init(self: *Self, allocator: std.mem.Allocator) void { + if (self.stack == null) { + self.stack = std.ArrayList(T).init(allocator); + } + } + + // 析构函数(释放内存) + pub fn deinit(self: *Self) void { + if (self.stack == null) return; + self.stack.?.deinit(); + } + + // 获取栈的长度 + pub fn size(self: *Self) usize { + return self.stack.?.items.len; + } + + // 判断栈是否为空 + pub fn isEmpty(self: *Self) bool { + return self.size() == 0; + } + + // 访问栈顶元素 + pub fn peek(self: *Self) T { + if (self.isEmpty()) @panic("栈为空"); + return self.stack.?.items[self.size() - 1]; + } + + // 入栈 + pub fn push(self: *Self, num: T) !void { + try self.stack.?.append(num); + } + + // 出栈 + pub fn pop(self: *Self) T { + var num = self.stack.?.pop(); + return num; + } + + // 返回 ArrayList + pub fn toList(self: *Self) std.ArrayList(T) { + return self.stack.?; + } + }; + } ``` ## 5.1.3. 两种实现对比 diff --git a/chapter_tree/avl_tree.md b/chapter_tree/avl_tree.md index 4f57c4263..45be7f0ab 100644 --- a/chapter_tree/avl_tree.md +++ b/chapter_tree/avl_tree.md @@ -303,7 +303,18 @@ G. M. Adelson-Velsky 和 E. M. Landis 在其 1962 年发表的论文 "An algorit === "Zig" ```zig title="avl_tree.zig" + // 获取结点高度 + fn height(self: *Self, node: ?*inc.TreeNode(T)) i32 { + _ = self; + // 空结点高度为 -1 ,叶结点高度为 0 + return if (node == null) -1 else node.?.height; + } + // 更新结点高度 + fn updateHeight(self: *Self, node: ?*inc.TreeNode(T)) void { + // 结点高度等于最高子树高度 + 1 + node.?.height = std.math.max(self.height(node.?.left), self.height(node.?.right)) + 1; + } ``` ### 结点平衡因子 @@ -420,7 +431,13 @@ G. M. Adelson-Velsky 和 E. M. Landis 在其 1962 年发表的论文 "An algorit === "Zig" ```zig title="avl_tree.zig" - + // 获取平衡因子 + fn balanceFactor(self: *Self, node: ?*inc.TreeNode(T)) i32 { + // 空结点平衡因子为 0 + if (node == null) return 0; + // 结点平衡因子 = 左子树高度 - 右子树高度 + return self.height(node.?.left) - self.height(node.?.right); + } ``` !!! note @@ -608,7 +625,19 @@ AVL 树的独特之处在于「旋转 Rotation」的操作,其可 **在不影 === "Zig" ```zig title="avl_tree.zig" - + // 右旋操作 + fn rightRotate(self: *Self, node: ?*inc.TreeNode(T)) ?*inc.TreeNode(T) { + var child = node.?.left; + var grandChild = child.?.right; + // 以 child 为原点,将 node 向右旋转 + child.?.right = node; + node.?.left = grandChild; + // 更新结点高度 + self.updateHeight(node); + self.updateHeight(child); + // 返回旋转后子树的根结点 + return child; + } ``` ### Case 2 - 左旋 @@ -778,7 +807,19 @@ AVL 树的独特之处在于「旋转 Rotation」的操作,其可 **在不影 === "Zig" ```zig title="avl_tree.zig" - + // 左旋操作 + fn leftRotate(self: *Self, node: ?*inc.TreeNode(T)) ?*inc.TreeNode(T) { + var child = node.?.right; + var grandChild = child.?.left; + // 以 child 为原点,将 node 向左旋转 + child.?.left = node; + node.?.right = grandChild; + // 更新结点高度 + self.updateHeight(node); + self.updateHeight(child); + // 返回旋转后子树的根结点 + return child; + } ``` ### Case 3 - 先左后右 @@ -1100,7 +1141,35 @@ AVL 树的独特之处在于「旋转 Rotation」的操作,其可 **在不影 === "Zig" ```zig title="avl_tree.zig" - + // 执行旋转操作,使该子树重新恢复平衡 + fn rotate(self: *Self, node: ?*inc.TreeNode(T)) ?*inc.TreeNode(T) { + // 获取结点 node 的平衡因子 + var balance_factor = self.balanceFactor(node); + // 左偏树 + if (balance_factor > 1) { + if (self.balanceFactor(node.?.left) >= 0) { + // 右旋 + return self.rightRotate(node); + } else { + // 先左旋后右旋 + node.?.left = self.leftRotate(node.?.left); + return self.rightRotate(node); + } + } + // 右偏树 + if (balance_factor < -1) { + if (self.balanceFactor(node.?.right) <= 0) { + // 左旋 + return self.leftRotate(node); + } else { + // 先右旋后左旋 + node.?.right = self.rightRotate(node.?.right); + return self.leftRotate(node); + } + } + // 平衡树,无需旋转,直接返回 + return node; + } ``` ## 7.4.3. AVL 树常用操作 @@ -1345,7 +1414,34 @@ AVL 树的独特之处在于「旋转 Rotation」的操作,其可 **在不影 === "Zig" ```zig title="avl_tree.zig" + // 插入结点 + fn insert(self: *Self, val: T) !?*inc.TreeNode(T) { + self.root = try self.insertHelper(self.root, val); + return self.root; + } + // 递归插入结点(辅助函数) + fn insertHelper(self: *Self, node_: ?*inc.TreeNode(T), val: T) !?*inc.TreeNode(T) { + var node = node_; + if (node == null) { + var tmp_node = try self.mem_allocator.create(inc.TreeNode(T)); + tmp_node.init(val); + return tmp_node; + } + // 1. 查找插入位置,并插入结点 + if (val < node.?.val) { + node.?.left = try self.insertHelper(node.?.left, val); + } else if (val > node.?.val) { + node.?.right = try self.insertHelper(node.?.right, val); + } else { + return node; // 重复结点不插入,直接返回 + } + self.updateHeight(node); // 更新结点高度 + // 2. 执行旋转操作,使该子树重新恢复平衡 + node = self.rotate(node); + // 返回子树的根结点 + return node; + } ``` ### 删除结点 @@ -1790,7 +1886,56 @@ AVL 树的独特之处在于「旋转 Rotation」的操作,其可 **在不影 === "Zig" ```zig title="avl_tree.zig" + // 删除结点 + fn remove(self: *Self, val: T) ?*inc.TreeNode(T) { + self.root = self.removeHelper(self.root, val); + return self.root; + } + // 递归删除结点(辅助函数) + fn removeHelper(self: *Self, node_: ?*inc.TreeNode(T), val: T) ?*inc.TreeNode(T) { + var node = node_; + if (node == null) return null; + // 1. 查找结点,并删除之 + if (val < node.?.val) { + node.?.left = self.removeHelper(node.?.left, val); + } else if (val > node.?.val) { + node.?.right = self.removeHelper(node.?.right, val); + } else { + if (node.?.left == null or node.?.right == null) { + var child = if (node.?.left != null) node.?.left else node.?.right; + // 子结点数量 = 0 ,直接删除 node 并返回 + if (child == null) { + return null; + // 子结点数量 = 1 ,直接删除 node + } else { + node = child; + } + } else { + // 子结点数量 = 2 ,则将中序遍历的下个结点删除,并用该结点替换当前结点 + var temp = self.getInOrderNext(node.?.right); + node.?.right = self.removeHelper(node.?.right, temp.?.val); + node.?.val = temp.?.val; + } + } + self.updateHeight(node); // 更新结点高度 + // 2. 执行旋转操作,使该子树重新恢复平衡 + node = self.rotate(node); + // 返回子树的根结点 + return node; + } + + // 获取中序遍历中的下一个结点(仅适用于 root 有左子结点的情况) + fn getInOrderNext(self: *Self, node_: ?*inc.TreeNode(T)) ?*inc.TreeNode(T) { + _ = self; + var node = node_; + if (node == null) return node; + // 循环访问左子结点,直到叶结点时为最小结点,跳出 + while (node.?.left != null) { + node = node.?.left; + } + return node; + } ``` ### 查找结点 diff --git a/chapter_tree/binary_search_tree.md b/chapter_tree/binary_search_tree.md index 298bc9044..cdf825125 100755 --- a/chapter_tree/binary_search_tree.md +++ b/chapter_tree/binary_search_tree.md @@ -217,7 +217,25 @@ comments: true === "Zig" ```zig title="binary_search_tree.zig" - + // 查找结点 + fn search(self: *Self, num: T) ?*inc.TreeNode(T) { + var cur = self.root; + // 循环查找,越过叶结点后跳出 + while (cur != null) { + // 目标结点在 cur 的右子树中 + if (cur.?.val < num) { + cur = cur.?.right; + // 目标结点在 cur 的左子树中 + } else if (cur.?.val > num) { + cur = cur.?.left; + // 找到目标结点,跳出循环 + } else { + break; + } + } + // 返回目标结点 + return cur; + } ``` ### 插入结点 @@ -490,7 +508,35 @@ comments: true === "Zig" ```zig title="binary_search_tree.zig" - + // 插入结点 + fn insert(self: *Self, num: T) !?*inc.TreeNode(T) { + // 若树为空,直接提前返回 + if (self.root == null) return null; + var cur = self.root; + var pre: ?*inc.TreeNode(T) = null; + // 循环查找,越过叶结点后跳出 + while (cur != null) { + // 找到重复结点,直接返回 + if (cur.?.val == num) return null; + pre = cur; + // 插入位置在 cur 的右子树中 + if (cur.?.val < num) { + cur = cur.?.right; + // 插入位置在 cur 的左子树中 + } else { + cur = cur.?.left; + } + } + // 插入结点 val + var node = try self.mem_allocator.create(inc.TreeNode(T)); + node.init(num); + if (pre.?.val < num) { + pre.?.right = node; + } else { + pre.?.left = node; + } + return node; + } ``` 为了插入结点,需要借助 **辅助结点 `pre`** 保存上一轮循环的结点,这样在遍历到 $\text{null}$ 时,我们也可以获取到其父结点,从而完成结点插入操作。 @@ -1024,7 +1070,61 @@ comments: true === "Zig" ```zig title="binary_search_tree.zig" + // 删除结点 + fn remove(self: *Self, num: T) ?*inc.TreeNode(T) { + // 若树为空,直接提前返回 + if (self.root == null) return null; + var cur = self.root; + var pre: ?*inc.TreeNode(T) = null; + // 循环查找,越过叶结点后跳出 + while (cur != null) { + // 找到待删除结点,跳出循环 + if (cur.?.val == num) break; + pre = cur; + // 待删除结点在 cur 的右子树中 + if (cur.?.val < num) { + cur = cur.?.right; + // 待删除结点在 cur 的左子树中 + } else { + cur = cur.?.left; + } + } + // 若无待删除结点,则直接返回 + if (cur == null) return null; + // 子结点数量 = 0 or 1 + if (cur.?.left == null or cur.?.right == null) { + // 当子结点数量 = 0 / 1 时, child = null / 该子结点 + var child = if (cur.?.left != null) cur.?.left else cur.?.right; + // 删除结点 cur + if (pre.?.left == cur) { + pre.?.left = child; + } else { + pre.?.right = child; + } + // 子结点数量 = 2 + } else { + // 获取中序遍历中 cur 的下一个结点 + var nex = self.getInOrderNext(cur.?.right); + var tmp = nex.?.val; + // 递归删除结点 nex + _ = self.remove(nex.?.val); + // 将 nex 的值复制给 cur + cur.?.val = tmp; + } + return cur; + } + // 获取中序遍历中的下一个结点(仅适用于 root 有左子结点的情况) + fn getInOrderNext(self: *Self, node: ?*inc.TreeNode(T)) ?*inc.TreeNode(T) { + _ = self; + var node_tmp = node; + if (node_tmp == null) return null; + // 循环访问左子结点,直到叶结点时为最小结点,跳出 + while (node_tmp.?.left != null) { + node_tmp = node_tmp.?.left; + } + return node_tmp; + } ``` ### 排序 diff --git a/chapter_tree/binary_tree_traversal.md b/chapter_tree/binary_tree_traversal.md index b78b9a491..8804a5d6d 100755 --- a/chapter_tree/binary_tree_traversal.md +++ b/chapter_tree/binary_tree_traversal.md @@ -211,7 +211,33 @@ comments: true === "Zig" ```zig title="binary_tree_bfs.zig" - + // 层序遍历 + fn hierOrder(comptime T: type, mem_allocator: std.mem.Allocator, root: *inc.TreeNode(T)) !std.ArrayList(T) { + // 初始化队列,加入根结点 + const L = std.TailQueue(*inc.TreeNode(T)); + var queue = L{}; + var root_node = try mem_allocator.create(L.Node); + root_node.data = root; + queue.append(root_node); + // 初始化一个列表,用于保存遍历序列 + var list = std.ArrayList(T).init(std.heap.page_allocator); + while (queue.len > 0) { + var queue_node = queue.popFirst().?; // 队列出队 + var node = queue_node.data; + try list.append(node.val); // 保存结点值 + if (node.left != null) { + var tmp_node = try mem_allocator.create(L.Node); + tmp_node.data = node.left.?; + queue.append(tmp_node); // 左子结点入队 + } + if (node.right != null) { + var tmp_node = try mem_allocator.create(L.Node); + tmp_node.data = node.right.?; + queue.append(tmp_node); // 右子结点入队 + } + } + return list; + } ``` ## 7.2.2. 前序、中序、后序遍历 @@ -512,7 +538,32 @@ comments: true === "Zig" ```zig title="binary_tree_dfs.zig" + // 前序遍历 + fn preOrder(comptime T: type, root: ?*inc.TreeNode(T)) !void { + if (root == null) return; + // 访问优先级:根结点 -> 左子树 -> 右子树 + try list.append(root.?.val); + try preOrder(T, root.?.left); + try preOrder(T, root.?.right); + } + // 中序遍历 + fn inOrder(comptime T: type, root: ?*inc.TreeNode(T)) !void { + if (root == null) return; + // 访问优先级:左子树 -> 根结点 -> 右子树 + try inOrder(T, root.?.left); + try list.append(root.?.val); + try inOrder(T, root.?.right); + } + + // 后序遍历 + fn postOrder(comptime T: type, root: ?*inc.TreeNode(T)) !void { + if (root == null) return; + // 访问优先级:左子树 -> 右子树 -> 根结点 + try postOrder(T, root.?.left); + try postOrder(T, root.?.right); + try list.append(root.?.val); + } ``` !!! note