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

題目描述

思路

遞迴，深度優先
使用陣列儲存對應層的最大值

程式碼

#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;

}