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krahets
2023-06-25 21:11:35 +08:00
parent 5bc8df6d5d
commit e4e6cd6bae
19 changed files with 836 additions and 105 deletions
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42
chapter_hashing/hash_map.md
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@@ -1212,7 +1212,7 @@ index = hash(key) % capacity
key: usize = undefined,
val: []const u8 = undefined,
pub fn init(key: usize, val: []const u8) Pair {
pub fn init(key: usize, val: []const u8) Pair {
return Pair {
.key = key,
.val = val,
@@ -1223,25 +1223,25 @@ index = hash(key) % capacity
// 基于数组简易实现的哈希表
fn ArrayHashMap(comptime T: type) type {
return struct {
buckets: ?std.ArrayList(?T) = null,
bucket: ?std.ArrayList(?T) = null,
mem_allocator: std.mem.Allocator = undefined,
const Self = @This();
// 构造方法
// 构造函数
pub fn init(self: *Self, allocator: std.mem.Allocator) !void {
self.mem_allocator = allocator;
// 初始化数组，包含 100 个桶
self.buckets = std.ArrayList(?T).init(self.mem_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.buckets.?.append(null);
try self.bucket.?.append(null);
}
}
// 析构方法
// 析构函数
pub fn deinit(self: *Self) void {
if (self.buckets != null) self.buckets.?.deinit();
if (self.bucket != null) self.bucket.?.deinit();
}
// 哈希函数
@@ -1253,7 +1253,7 @@ index = hash(key) % capacity
// 查询操作
pub fn get(self: *Self, key: usize) []const u8 {
var index = hashFunc(key);
var pair = self.buckets.?.items[index];
var pair = self.bucket.?.items[index];
return pair.?.val;
}
@@ -1261,44 +1261,44 @@ index = hash(key) % capacity
pub fn put(self: *Self, key: usize, val: []const u8) !void {
var pair = Pair.init(key, val);
var index = hashFunc(key);
self.buckets.?.items[index] = pair;
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.buckets.?.items[index] = null;
self.bucket.?.items[index] = null;
}
// 获取所有键值对
pub fn pairSet(self: *Self) !*std.ArrayList(T) {
pub fn pairSet(self: *Self) !std.ArrayList(T) {
var entry_set = std.ArrayList(T).init(self.mem_allocator);
for (self.buckets.?.items) |item| {
for (self.bucket.?.items) |item| {
if (item == null) continue;
try entry_set.append(item.?);
}
return &entry_set;
return entry_set;
}
// 获取所有键
pub fn keySet(self: *Self) !*std.ArrayList(usize) {
pub fn keySet(self: *Self) !std.ArrayList(usize) {
var key_set = std.ArrayList(usize).init(self.mem_allocator);
for (self.buckets.?.items) |item| {
for (self.bucket.?.items) |item| {
if (item == null) continue;
try key_set.append(item.?.key);
}
return &key_set;
return key_set;
}
// 获取所有值
pub fn valueSet(self: *Self) !*std.ArrayList([]const u8) {
pub fn valueSet(self: *Self) !std.ArrayList([]const u8) {
var value_set = std.ArrayList([]const u8).init(self.mem_allocator);
for (self.buckets.?.items) |item| {
for (self.bucket.?.items) |item| {
if (item == null) continue;
try value_set.append(item.?.val);
}
return &value_set;
return value_set;
}
// 打印哈希表
@@ -1405,7 +1405,7 @@ index = hash(key) % capacity
## 6.1.3. &nbsp; 哈希冲突与扩容
本质上看，哈希函数的作用是黄输入空间（`key` 范围）映射到输出空间（数组索引范围），而输入空间往往远大于输出空间。因此，**理论上一定存在“多个输入对应相同输出”的情况**。
本质上看，哈希函数的作用是将输入空间（`key` 范围）映射到输出空间（数组索引范围），而输入空间往往远大于输出空间。因此，**理论上一定存在“多个输入对应相同输出”的情况**。
对于上述示例中的哈希函数，当输入的 `key` 后两位相同时，哈希函数的输出结果也相同。例如，查询学号为 12836 和 20336 的两个学生时，我们得到：