題目描述

思路

一招層序歷遍走遍天下。

解答

/**
 * 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:
    vector<int> largestValues(TreeNode*
 
 root) {
        vector<int> res;
        if(!root) return res;
        queue<TreeNode*> q;
        q.push(root);
        while(!q.empty())
        {
            auto size = q.size();
            int cur = q.front()->val;
            while(size--)
            {
                TreeNode*
 
 temp = q.front();
                q.pop();   //一開始忘記寫這句，導致記憶體溢位
                if(temp->val > cur) cur = temp->val;
                if(temp->left) q.push(temp->left);
                if(temp->right) q.push(temp->right);
            }
            res.push_back(cur);
        }
        return
 
 res;
    }
};