[LeetCode]515. Find Largest Value in Each Tree Row

题目描述

思路

递归，深度优先
使用数组存储对应层的最大值

代码

#include <iostream>#include <vector>#include <algorithm>using namespace std;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 == NULL) return res;        res.push_back(root->val);        travel(root, 0, res);        return res;    }private:    void travel(TreeNode* root, int level, vector<int>& res) {        if (root == NULL) return;        if (level < res.size()) res[level] = max(res[level], root->val);        else res.push_back(root->val);        travel(root->left, level + 1, res);        travel(root->right, level + 1, res);    }};int main() {    TreeNode* t1 = new TreeNode(1);    TreeNode* t2 = new TreeNode(3);    TreeNode* t3 = new TreeNode(2);    TreeNode* t4 = new TreeNode(5);    TreeNode* t5 = new TreeNode(3);    TreeNode* t6 = new TreeNode(9);    t1->left = t2;    t1->right = t3;    t2->left = t4;    t2->right = t5;    t3->right = t6;    Solution s;    vector<int> res = s.largestValues(t1);    for (int num : res)        cout << num << " ";    cout << endl;    system("pause");    return 0;}