[LeetCode]515 Find Largest Value in Each Tree Row（dfs）

题目链接：https://leetcode.com/problems/find-largest-value-in-each-tree-row/?tab=Description

题意：找每层的最大值。

直接dfs扔map里

 1 class Solution {
 2 public:
 3     int sz;
 4     map<int, int> ret;
 5     void dfs(TreeNode* p, int d) {
 6         sz = max(sz, d);
 7         if(ret.find(d) == ret.end()) ret[d] = p->val;
 8         else ret[d] = max(ret[d], p->val);
 9         if(p->left) dfs(p->left, d+1);
10         if(p->right) dfs(p->right, d+1);
11     }
12     vector<int> largestValues(TreeNode* root) {
13         ret.clear();
14         sz = -1;
15         if(root == NULL) return vector<int>();
16         dfs(root, 0);
17         vector<int> v;
18         for(int i = 0; i <= sz; i++) v.push_back(ret[i]);
19         return v;
20     }
21 };