Maximum Level Sum of a Binary Tree（C++ 最大层内元素和）

素颜马尾好姑娘i 2023-01-03 12:53 191阅读 0赞

解题思路：

（1）使用map记录每层元素的和

（2）分层比较大小

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
 *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
 * };
 */
class Solution {
public:
    void pre_order(TreeNode *root,int h,unordered_map<int,int> &mp) {
        if(root==NULL) return;
        mp[h]+=root->val;
        pre_order(root->left,h+1,mp);
        pre_order(root->right,h+1,mp);
    }
    int maxLevelSum(TreeNode* root) {
        unordered_map<int,int> mp;
        pre_order(root,1,mp);
        int level=-1,max=-100001;
        for(auto it=mp.begin();it!=mp.end();it++) {
            if(it->second>=max) {
                max=it->second;
                level=it->first;
            } 
        }
        return level;
    }
};