[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

class Solution {
public:
    int sz;
    map<int, int> ret;
    void dfs(TreeNode* p, int d) {
        sz = max(sz, d);
        if(ret.find(d) == ret.end()) ret[d] = p->val;
        else ret[d] = max(ret[d], p->val);
        if(p->left) dfs(p->left, d+1);
        if(p->right) dfs(p->right, d+1);
    }
    vector<int> largestValues(TreeNode* root) {
        ret.clear();
        sz = -1;
        if(root == NULL) return vector<int>();
        dfs(root, 0);
        vector<int> v;
        for(int i = 0; i <= sz; i++) v.push_back(ret[i]);
        return v;
    }
};