Cousins in Binary Tree.java

// Runtime: 0 ms (Top 100.0%) | Memory: 41.30 MB (Top 42.36%)

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode() {}
 *     TreeNode(int val) { this.val = val; }
 *     TreeNode(int val, TreeNode left, TreeNode right) {
 *         this.val = val;
 *         this.left = left;
 *         this.right = right;
 *     }
 * }
 */
class Solution {
    public boolean isCousins(TreeNode root, int x, int y) {
        
        //If any of x or y is at root, it means they can't be at same depth. Return false.
        if(root.val == x || root.val == y) return false;
        
        
        Deque<TreeNode> queue = new LinkedList<>();
        queue.offer(root);
        
        boolean xFound = false;
        boolean yFound = false;
        
        int parentX = 0;
        int parentY = 0;
        
        //Do level-order traversal until x or y is found or queue is empty.
        while(!queue.isEmpty() && !xFound && !yFound){
            
            int size = queue.size();
			
            //Traverse that level.
            while(size-- > 0){
                TreeNode node = queue.poll();
				
                //if x or y is found at left/right, save the parent and set the "found" flag to true.
                //This flag will break the loop as soon as any one (x or y) is found. 
				//we don't need to go deeper to find second if it isn't found at this level.
				
                if(node.left != null) {
                    queue.offer(node.left);
                    
                    if(node.left.val == x){
                        parentX = node.val;
                        xFound = true;
                    }
                    if(node.left.val == y){
                        parentY = node.val;
                        yFound = true;
                    }
                    
                }

                if(node.right != null) {
                    queue.offer(node.right);
                    
                    if(node.right.val == x){
                        parentX = node.val;
                        xFound = true;
                    }
                    if(node.right.val == y){
                        parentY = node.val;
                        yFound = true;
                    }
                }
            }
            
        }
        return xFound && yFound && parentX != parentY;
    }
}