2026/04/15

[LeetCode] 235 Lowest Common Ancestor of a Binary Search Tree

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/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */

class Solution {
public:
  TreeNode* LCABST(TreeNode* cur, TreeNode* p, TreeNode* q) {
    if (cur->val > p->val && cur->val > q->val)
      return LCABST(cur->left, p, q);
    if (cur->val < p->val && cur->val < q->val)
      return LCABST(cur->right, p, q);
    return cur;
  }

  TreeNode* lowestCommonAncestor(TreeNode* root, TreeNode* p, TreeNode* q) {
    return LCABST(root, p, q);
  }
};