leetcode 515.在每个树行中找最大值

/**
 * 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:
    vector<int> largestValues(TreeNode* root) {
        queue<TreeNode*> q;
        vector<vector<int>> res;
        if(root!=NULL) q.push(root);
        while(!q.empty()){
            int len=q.size();
            vector<int> vec;
            for(int i=0;i<len;i++){
                TreeNode* cur=q.front();
                q.pop();
                int curN=cur->val;
                vec.push_back(curN);
                if(cur->left!=NULL) q.push(cur->left);
                if(cur->right!=NULL) q.push(cur->right);

            }
            res.push_back(vec);


        }
        vector<int> result;
        for(int i=0;i<res.size();i++){
            int max=INT_MIN;
            for(int j=0;j<res[i].size();j++){
                if(max<res[i][j]){
                    max=res[i][j];
                }
            }
            result.push_back(max);
        }
        return result;
        
    }
};