Pseudo-Palindromic Paths in a Binary Tree.java

/**
 * 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 {
    int ans =0;
    public int pseudoPalindromicPaths (TreeNode root) {
        func(root, 0);
        return ans;
    }
    void func(TreeNode node, int seen){
        if(node == null) return;
        // System.out.println("b4 " + Integer.toBinaryString(seen));
        seen^=(1<<node.val);
        // System.out.println("after " + Integer.toBinaryString(seen));
        if(node.left == null && node.right == null){
            if((seen & (seen-1)) == 0){
                ans++;
            }
            return;
        }
        func(node.left, seen);
        func(node.right, seen);

    }
}