Day 7 Cousins in Binary Tree.cpp

PROBLEM:


In a binary tree, the root node is at depth 0, and children of each depth k node are at depth k+1.
Two nodes of a binary tree are cousins if they have the same depth, but have different parents.
We are given the root of a binary tree with unique values, and the values x and y of two different nodes in the tree.
Return true if and only if the nodes corresponding to the values x and y are cousins.

Example 1:
Input: root = [1,2,3,4], x = 4, y = 3
Output: false

Example 2:
Input: root = [1,2,3,null,4,null,5], x = 5, y = 4
Output: true

Example 3:
Input: root = [1,2,3,null,4], x = 2, y = 3
Output: false
 

Note:

The number of nodes in the tree will be between 2 and 100.
Each node has a unique integer value from 1 to 100.


SOLUTION:


class Solution {
public:
    bool isCousins(TreeNode* root, int x, int y) {
        unordered_map<int,pair<int,int>> m;
        
        helper(root,0,-1,m);
        
        if(m[x].first == m[y].first && m[x].second != m[y].second)
            return true;
        else
            return false;
    }
    
    void helper(TreeNode* root,int depth,int parent,unordered_map<int,pair<int,int>>& m)
    {
        if(root==NULL)
            return ;
        
        m[root->val]={depth,parent};
        
        helper(root->left,depth+1,root->val,m);
        helper(root->right,depth+1,root->val,m);
        
    }
};