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Add missing Dart codes and fix some errors (#689)

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* Add missing Dart codes and fix some errors

* Update array_binary_tree.dart

---------

Co-authored-by: Yudong Jin <krahets@163.com>
This commit is contained in:
liuyuxin
2023-08-17 05:04:38 +08:00
committed by GitHub
parent 5d7e0a59b1
commit 0858ab91c0
14 changed files with 504 additions and 204 deletions
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235
codes/dart/chapter_tree/binary_search_tree.dart
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@@ -8,122 +8,125 @@ import '../utils/print_util.dart';
import '../utils/tree_node.dart';
/* 二叉搜索树 */
TreeNode? root;
class BinarySearchTree {
late TreeNode? _root;
void binarySearchTree(List<int> nums) {
nums.sort(); // 排序数组
root = buildTree(nums, 0, nums.length - 1); // 构建二叉搜索树
}
/* 获取二叉树的根节点 */
TreeNode? getRoot() {
return root;
}
/* 构建二叉上搜索树 */
TreeNode? buildTree(List<int> nums, int i, int j) {
if (i > j) {
return null;
/* 构造方法 */
BinarySearchTree(List<int> nums) {
nums.sort(); // 排序数组
_root = buildTree(nums, 0, nums.length - 1); // 构建二叉搜索树
}
// 将数组中间节点作为根节点
int mid = (i + j) ~/ 2;
TreeNode? root = TreeNode(nums[mid]);
root.left = buildTree(nums, i, mid - 1);
root.right = buildTree(nums, mid + 1, j);
return root;
}
/* 查找节点 */
TreeNode? search(int num) {
TreeNode? cur = root;
// 循环查找，越过叶节点后跳出
while (cur != null) {
// 目标节点在 cur 的右子树中
if (cur.val < num)
cur = cur.right;
// 目标节点在 cur 的左子树中
else if (cur.val > num)
cur = cur.left;
// 找到目标节点，跳出循环
/* 获取二叉树的根节点 */
TreeNode? getRoot() {
return _root;
}
/* 构建二叉上搜索树 */
TreeNode? buildTree(List<int> nums, int i, int j) {
if (i > j) {
return null;
}
// 将数组中间节点作为根节点
int mid = (i + j) ~/ 2;
TreeNode? root = TreeNode(nums[mid]);
root.left = buildTree(nums, i, mid - 1);
root.right = buildTree(nums, mid + 1, j);
return root;
}
/* 查找节点 */
TreeNode? search(int num) {
TreeNode? cur = _root;
// 循环查找，越过叶节点后跳出
while (cur != null) {
// 目标节点在 cur 的右子树中
if (cur.val < num)
cur = cur.right;
// 目标节点在 cur 的左子树中
else if (cur.val > num)
cur = cur.left;
// 找到目标节点，跳出循环
else
break;
}
// 返回目标节点
return cur;
}
/* 插入节点 */
void insert(int num) {
// 若树为空，直接提前返回
if (_root == null) return;
TreeNode? cur = _root;
TreeNode? pre = null;
// 循环查找，越过叶节点后跳出
while (cur != null) {
// 找到重复节点，直接返回
if (cur.val == num) return;
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;
}
// 插入节点
TreeNode? node = TreeNode(num);
if (pre!.val < num)
pre.right = node;
else
break;
pre.left = node;
}
// 返回目标节点
return cur;
}
/* 插入节点 */
void insert(int num) {
// 若树为空，直接提前返回
if (root == null) return;
TreeNode? cur = root;
TreeNode? pre = null;
// 循环查找，越过叶节点后跳出
while (cur != null) {
// 找到重复节点，直接返回
if (cur.val == num) return;
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;
}
// 插入节点
TreeNode? node = TreeNode(num);
if (pre!.val < num)
pre.right = node;
else
pre.left = node;
}
/* 删除节点 */
void remove(int num) {
// 若树为空，直接提前返回
if (root == null) return;
void remove(int num) {
// 若树为空，直接提前返回
if (_root == null) return;
TreeNode? cur = root;
TreeNode? pre = null;
// 循环查找，越过叶节点后跳出
while (cur != null) {
// 找到待删除节点，跳出循环
if (cur.val == num) break;
pre = cur;
// 待删除节点在 cur 的右子树中
if (cur.val < num)
cur = cur.right;
// 待删除节点在 cur 的左子树中
else
cur = cur.left;
}
// 若无待删除节点，直接返回
if (cur == null) return;
// 子节点数量 = 0 or 1
if (cur.left == null || cur.right == null) {
// 当子节点数量 = 0 / 1 时， child = null / 该子节点
TreeNode? child = cur.left ?? cur.right;
// 删除节点 cur
if (cur != root) {
if (pre!.left == cur)
pre.left = child;
TreeNode? cur = _root;
TreeNode? pre = null;
// 循环查找，越过叶节点后跳出
while (cur != null) {
// 找到待删除节点，跳出循环
if (cur.val == num) break;
pre = cur;
// 待删除节点在 cur 的右子树中
if (cur.val < num)
cur = cur.right;
// 待删除节点在 cur 的左子树中
else
pre.right = child;
cur = cur.left;
}
// 若无待删除节点，直接返回
if (cur == null) return;
// 子节点数量 = 0 or 1
if (cur.left == null || cur.right == null) {
// 当子节点数量 = 0 / 1 时， child = null / 该子节点
TreeNode? child = cur.left ?? cur.right;
// 删除节点 cur
if (cur != _root) {
if (pre!.left == cur)
pre.left = child;
else
pre.right = child;
} else {
// 若删除节点为根节点，则重新指定根节点
_root = child;
}
} else {
// 若删除节点为根节点，则重新指定根节点
root = child;
// 子节点数量 = 2
// 获取中序遍历中 cur 的下一个节点
TreeNode? tmp = cur.right;
while (tmp!.left != null) {
tmp = tmp.left;
}
// 递归删除节点 tmp
remove(tmp.val);
// 用 tmp 覆盖 cur
cur.val = tmp.val;
}
} else {
// 子节点数量 = 2
// 获取中序遍历中 cur 的下一个节点
TreeNode? tmp = cur.right;
while (tmp!.left != null) {
tmp = tmp.left;
}
// 递归删除节点 tmp
remove(tmp.val);
// 用 tmp 覆盖 cur
cur.val = tmp.val;
}
}
@@ -131,27 +134,27 @@ void remove(int num) {
void main() {
/* 初始化二叉搜索树 */
List<int> nums = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15];
binarySearchTree(nums);
BinarySearchTree bst = BinarySearchTree(nums);
print("\n初始化的二叉树为\n");
printTree(getRoot());
printTree(bst.getRoot());
/* 查找节点 */
TreeNode? node = search(7);
TreeNode? node = bst.search(7);
print("\n查找到的节点对象为 $node，节点值 = ${node?.val}");
/* 插入节点 */
insert(16);
bst.insert(16);
print("\n插入节点 16 后，二叉树为\n");
printTree(getRoot());
printTree(bst.getRoot());
/* 删除节点 */
remove(1);
bst.remove(1);
print("\n删除节点 1 后，二叉树为\n");
printTree(getRoot());
remove(2);
printTree(bst.getRoot());
bst.remove(2);
print("\n删除节点 2 后，二叉树为\n");
printTree(getRoot());
remove(4);
printTree(bst.getRoot());
bst.remove(4);
print("\n删除节点 4 后，二叉树为\n");
printTree(getRoot());
printTree(bst.getRoot());
}