May-7 2020 Challenge

7. Cousins in Binary Tree

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:
Relates with leetcode may 7, 2020 Challenge

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

Example 2:

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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 IN JAVA :

class Solution {

Node xNode = new Node();
Node yNode = new Node();
int x, y;

public boolean isCousins(TreeNode root, int x, int y) {
this.x = x;
this.y = y;
preOrder(root, 0, 1);
return xNode.parent != yNode.parent && xNode.depth == yNode.depth;
}

private void preOrder(TreeNode root, int parent, int depth) {
if (root == null) {
return;
}

if (root.val == x) {
xNode.parent = parent;
xNode.depth = depth;
}
if (root.val == y) {
yNode.parent = parent;
yNode.depth = depth;
}
preOrder(root.left, root.val, depth + 1);
preOrder(root.right, root.val, depth + 1);
}

class Node {
int parent;
int depth;
}
}

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