# LeetCode - 0993. Cousins in Binary Tree（DFS 版）
### 題目網址：https://leetcode.com/problems/cousins-in-binary-tree/
###### tags: `LeetCode` `Easy` `圖論` `深度優先搜尋（Depth First Search）`

/*
    -LeetCode format-
    Problem: 993. Cousins in Binary Tree
    Difficulty: Easy
    
    by Inversionpeter
*/



/**
 * 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 {
    
    int depths[105] = {}, parents[105] = {}, nowDepth = 0;
    
    void DFS(TreeNode *nowNode) {
        depths[nowNode->val] = nowDepth;
        ++nowDepth;
        if (nowNode->left) {
            parents[nowNode->left->val] = nowNode->val;
            DFS(nowNode->left);
        }
        if (nowNode->right) {
            parents[nowNode->right->val] = nowNode->val;
            DFS(nowNode->right);
        }
        --nowDepth;
    }
    
public:
    bool isCousins(TreeNode* root, int x, int y) {
        DFS(root);
        return depths[x] == depths[y] && parents[x] != parents[y];
    }
};