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feat: add solutions to lc problem: No.0235 (doocs#4265)
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‎solution/0200-0299/0235.Lowest Common Ancestor of a Binary Search Tree/README.md

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@@ -32,7 +32,7 @@ tags:
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<p><strong>示例 1:</strong></p>
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<pre><strong>输入:</strong> root = [6,2,8,0,4,7,9,null,null,3,5], p = 2, q = 8
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<strong>输出:</strong> 6
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<strong>输出:</strong> 6
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<strong>解释: </strong>节点 <code>2 </code>和节点 <code>8 </code>的最近公共祖先是 <code>6。</code>
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</pre>
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<!-- solution:start -->
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### 方法一：迭代或递归
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### 方法一：迭代
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从上到下搜索，找到第一个值位于 $[p.val, q.val]$ 之间的结点即可。
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我们从根节点开始遍历，如果当前节点的值小于 $\textit{p}$ 和 $\textit{q}$ 的值，说明 $\textit{p}$ 和 $\textit{q}$ 应该在当前节点的右子树，因此将当前节点移动到右子节点；如果当前节点的值大于 $\textit{p}$ 和 $\textit{q}$ 的值，说明 $\textit{p}$ 和 $\textit{q}$ 应该在当前节点的左子树，因此将当前节点移动到左子节点；否则说明当前节点就是 $\textit{p}$ 和 $\textit{q}$ 的最近公共祖先，返回当前节点即可。
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既可以用迭代实现，也可以用递归实现。
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迭代的时间复杂度为 $O(n)$，空间复杂度为 $O(1)$。
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递归的时间复杂度为 $O(n)$，空间复杂度为 $O(n)$。
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时间复杂度 $O(n)$，其中 $n$ 是二叉搜索树的节点个数。空间复杂度 $O(1)$。
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<!-- tabs:start -->
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func lowestCommonAncestor(root, p, q *TreeNode) *TreeNode {
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for {
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if root.Val < p.Val && root.Val < q.Val {
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if root.Val < min(p.Val, q.Val) {
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root = root.Right
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} else if root.Val > p.Val && root.Val > q.Val {
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} else if root.Val > max(p.Val, q.Val) {
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root = root.Left
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} else {
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return root
@@ -209,13 +205,47 @@ function lowestCommonAncestor(
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}
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```
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#### C#
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```cs
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/**
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* Definition for a binary tree node.
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* public class TreeNode {
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* public int val;
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* public TreeNode left;
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* public TreeNode right;
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* public TreeNode(int x) { val = x; }
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* }
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*/
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public class Solution {
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public TreeNode LowestCommonAncestor(TreeNode root, TreeNode p, TreeNode q) {
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while (true) {
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if (root.val < Math.Min(p.val, q.val)) {
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root = root.right;
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} else if (root.val > Math.Max(p.val, q.val)) {
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root = root.left;
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} else {
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return root;
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}
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}
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}
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}
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```
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<!-- tabs:end -->
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<!-- solution:end -->
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<!-- solution:start -->
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### 方法二
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### 方法二：递归
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我们也可以使用递归的方法来解决这个问题。
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我们首先判断当前节点的值是否小于 $\textit{p}$ 和 $\textit{q}$ 的值，如果是，则递归遍历右子树；如果当前节点的值大于 $\textit{p}$ 和 $\textit{q}$ 的值，如果是，则递归遍历左子树；否则说明当前节点就是 $\textit{p}$ 和 $\textit{q}$ 的最近公共祖先，返回当前节点即可。
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时间复杂度 $O(n)$，空间复杂度 $O(n)$。其中 $n$ 是二叉搜索树的节点个数。
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<!-- tabs:start -->
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p: TreeNode | null,
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q: TreeNode | null,
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): TreeNode | null {
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if (root.val > p.val && root.val > q.val) return lowestCommonAncestor(root.left, p, q);
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if (root.val < p.val && root.val < q.val) return lowestCommonAncestor(root.right, p, q);
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if (root.val > p.val && root.val > q.val) {
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return lowestCommonAncestor(root.left, p, q);
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}
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if (root.val < p.val && root.val < q.val) {
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return lowestCommonAncestor(root.right, p, q);
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}
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return root;
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}
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```
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#### C#
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```cs
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/**
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* Definition for a binary tree node.
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* public class TreeNode {
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* public int val;
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* public TreeNode left;
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* public TreeNode right;
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* public TreeNode(int x) { val = x; }
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* }
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*/
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public class Solution {
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public TreeNode LowestCommonAncestor(TreeNode root, TreeNode p, TreeNode q) {
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if (root.val < Math.Min(p.val, q.val)) {
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return LowestCommonAncestor(root.right, p, q);
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}
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if (root.val > Math.Max(p.val, q.val)) {
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return LowestCommonAncestor(root.left, p, q);
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}
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return root;
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}
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}
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```
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<!-- tabs:end -->
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<!-- solution:end -->

‎solution/0200-0299/0235.Lowest Common Ancestor of a Binary Search Tree/README_EN.md

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<!-- solution:start -->
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### Solution 1
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### Solution 1: Iteration
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Starting from the root node, we traverse the tree. If the current node's value is less than both $\textit{p}$ and $\textit{q}$ values, it means that $\textit{p}$ and $\textit{q}$ should be in the right subtree of the current node, so we move to the right child. If the current node's value is greater than both $\textit{p}$ and $\textit{q}$ values, it means that $\textit{p}$ and $\textit{q}$ should be in the left subtree, so we move to the left child. Otherwise, it means the current node is the lowest common ancestor of $\textit{p}$ and $\textit{q}$, so we return the current node.
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The time complexity is $O(n)$, where $n$ is the number of nodes in the binary search tree. The space complexity is $O(1)$.
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<!-- tabs:start -->
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func lowestCommonAncestor(root, p, q *TreeNode) *TreeNode {
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for {
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if root.Val < p.Val && root.Val < q.Val {
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if root.Val < min(p.Val, q.Val) {
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root = root.Right
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} else if root.Val > p.Val && root.Val > q.Val {
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} else if root.Val > max(p.Val, q.Val) {
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root = root.Left
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} else {
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return root
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}
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```
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#### C#
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```cs
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/**
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* Definition for a binary tree node.
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* public class TreeNode {
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* public int val;
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* public TreeNode left;
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* public TreeNode right;
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* public TreeNode(int x) { val = x; }
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* }
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*/
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public class Solution {
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public TreeNode LowestCommonAncestor(TreeNode root, TreeNode p, TreeNode q) {
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while (true) {
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if (root.val < Math.Min(p.val, q.val)) {
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root = root.right;
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} else if (root.val > Math.Max(p.val, q.val)) {
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root = root.left;
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} else {
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return root;
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}
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}
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}
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}
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```
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<!-- tabs:end -->
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<!-- solution:end -->
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<!-- solution:start -->
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### Solution 2
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### Solution 2: Recursion
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We can also use a recursive approach to solve this problem.
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We first check if the current node's value is less than both $\textit{p}$ and $\textit{q}$ values. If it is, we recursively traverse the right subtree. If the current node's value is greater than both $\textit{p}$ and $\textit{q}$ values, we recursively traverse the left subtree. Otherwise, it means the current node is the lowest common ancestor of $\textit{p}$ and $\textit{q}$, so we return the current node.
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The time complexity is $O(n)$, and the space complexity is $O(n)$. Where $n$ is the number of nodes in the binary search tree.
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<!-- tabs:start -->
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p: TreeNode | null,
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q: TreeNode | null,
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): TreeNode | null {
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if (root.val > p.val && root.val > q.val) return lowestCommonAncestor(root.left, p, q);
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if (root.val < p.val && root.val < q.val) return lowestCommonAncestor(root.right, p, q);
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if (root.val > p.val && root.val > q.val) {
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return lowestCommonAncestor(root.left, p, q);
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}
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if (root.val < p.val && root.val < q.val) {
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return lowestCommonAncestor(root.right, p, q);
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}
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return root;
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}
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```
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#### C#
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```cs
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/**
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* Definition for a binary tree node.
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* public class TreeNode {
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* public int val;
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* public TreeNode left;
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* public TreeNode right;
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* public TreeNode(int x) { val = x; }
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* }
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*/
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public class Solution {
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public TreeNode LowestCommonAncestor(TreeNode root, TreeNode p, TreeNode q) {
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if (root.val < Math.Min(p.val, q.val)) {
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return LowestCommonAncestor(root.right, p, q);
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}
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if (root.val > Math.Max(p.val, q.val)) {
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return LowestCommonAncestor(root.left, p, q);
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}
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return root;
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}
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}
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```
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<!-- tabs:end -->
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<!-- solution:end -->

‎solution/0200-0299/0235.Lowest Common Ancestor of a Binary Search Tree/Solution.cs

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/**
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* Definition for a binary tree node.
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* public class TreeNode {
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* public int val;
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* public TreeNode left;
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* public TreeNode right;
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* public TreeNode(int x) { val = x; }
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* }
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*/
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public class Solution {
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public TreeNode LowestCommonAncestor(TreeNode root, TreeNode p, TreeNode q) {
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while (true) {
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if (root.val < Math.Min(p.val, q.val)) {
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root = root.right;
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} else if (root.val > Math.Max(p.val, q.val)) {
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root = root.left;
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} else {
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return root;
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}
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}
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}
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}

‎solution/0200-0299/0235.Lowest Common Ancestor of a Binary Search Tree/Solution.go

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func lowestCommonAncestor(root, p, q *TreeNode) *TreeNode {
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for {
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if root.Val < p.Val && root.Val < q.Val {
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if root.Val < min(p.Val, q.Val) {
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root = root.Right
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} else if root.Val > p.Val && root.Val > q.Val {
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} else if root.Val > max(p.Val, q.Val) {
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root = root.Left
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} else {
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return root
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}
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}
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}
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}

‎solution/0200-0299/0235.Lowest Common Ancestor of a Binary Search Tree/Solution2.cs

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/**
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* Definition for a binary tree node.
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* public class TreeNode {
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* public int val;
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* public TreeNode left;
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* public TreeNode right;
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* public TreeNode(int x) { val = x; }
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* }
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*/
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public class Solution {
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public TreeNode LowestCommonAncestor(TreeNode root, TreeNode p, TreeNode q) {
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if (root.val < Math.Min(p.val, q.val)) {
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return LowestCommonAncestor(root.right, p, q);
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}
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if (root.val > Math.Max(p.val, q.val)) {
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return LowestCommonAncestor(root.left, p, q);
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}
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return root;
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}
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}

‎solution/0200-0299/0235.Lowest Common Ancestor of a Binary Search Tree/Solution2.ts

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p: TreeNode | null,
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q: TreeNode | null,
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): TreeNode | null {
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if (root.val > p.val && root.val > q.val) return lowestCommonAncestor(root.left, p, q);
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if (root.val < p.val && root.val < q.val) return lowestCommonAncestor(root.right, p, q);
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if (root.val > p.val && root.val > q.val) {
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return lowestCommonAncestor(root.left, p, q);
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}
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if (root.val < p.val && root.val < q.val) {
24+
return lowestCommonAncestor(root.right, p, q);
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}
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return root;
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}

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