【LeetCode】LeetCode 236.二叉树的最近公共祖先

LeetCode 236.二叉树的最近公共祖先

题目链接：https://leetcode.cn/problems/lowest-common-ancestor-of-a-binary-tree/

题目

解答

求最小公共祖先，需要自底向上，如果是二叉树，那么只能通过后序遍历（即回溯）实现自底向上的遍历方式

class Solution {
public:
    TreeNode* lowestCommonAncestor(TreeNode* root, TreeNode* p, TreeNode* q) {
        if(root == p || root == q || root == NULL)  return root;
        TreeNode* left = lowestCommonAncestor(root->left, p, q);
        TreeNode* right = lowestCommonAncestor(root->right, p, q);

        if(left != NULL && right != NULL)   return root;
        if(left == NULL && right != NULL)   return right;
        return left;
    }
};