LeetCode || Lowest Common Ancestor of a Binary Tree

最新推荐文章于 2025-06-16 22:55:50 发布

原创最新推荐文章于 2025-06-16 22:55:50 发布 · 278 阅读

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本文详细介绍了如何使用栈和递归在二叉树中找到两个指定节点的最近公共祖先，通过构建路径并比较路径元素来实现这一目标。

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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:
    bool GetNodePath(TreeNode* from, TreeNode* to, stack<TreeNode*>& path)
    {
        path.push(from);
        if(from == to)
        {
            return true;
        }
        
        bool found = false;
        if(from->left!=NULL)
        {
            found = GetNodePath(from->left, to, path);
        }
        if(!found &&from->right!=NULL)
        {
            found = GetNodePath(from->right, to, path);
        }
        
        if(!found)
            path.pop();
        
        return found;
    }
    
    
    TreeNode* FindCommanNode(stack<TreeNode*>& p1, stack<TreeNode*>& p2)
    {
        while(p1.size() > p2.size())
            p1.pop();
        while(p2.size() > p1.size())
            p2.pop();
        while(p2.size() == p1.size() && p2.top() != p1.top())
        {
            p2.pop();
            p1.pop();
        }
        return p1.top();
    }
    
    TreeNode* lowestCommonAncestor(TreeNode* root, TreeNode* p, TreeNode* q) {
        
        if(root == NULL || p == NULL || q == NULL)
            return NULL;
        stack<TreeNode*> Pathp, Pathq, curr;
        curr.push(root);
        GetNodePath(root, p, Pathp);
        GetNodePath(root, q, Pathq);
        
        return FindCommanNode(Pathp, Pathq);
        
    }
};