_563.java

package com.fishercoder.solutions;

import com.fishercoder.common.classes.TreeNode;

/**
 * 563. Binary Tree Tilt
 *
 * Given a binary tree, return the tilt of the whole tree.
 * The tilt of a tree node is defined as the absolute difference between the sum of all left subtree node values
 * and the sum of all right subtree node values.
 * Null node has tilt 0.
 * The tilt of the whole tree is defined as the sum of all nodes' tilt.

 Example:
 Input:
    1
  /   \
 2     3

 Output: 1

 Explanation:
 Tilt of node 2 : 0
 Tilt of node 3 : 0
 Tilt of node 1 : |2-3| = 1
 Tilt of binary tree : 0 + 0 + 1 = 1

 Note:
 The sum of node values in any subtree won't exceed the range of 32-bit integer.
 All the tilt values won't exceed the range of 32-bit integer.*/
public class _563 {
    public static class Solution1 {

        int tilt = 0;

        public int findTilt(TreeNode root) {
            findTiltDfs(root);
            return tilt;
        }

        public int findTiltDfs(TreeNode root) {
            if (root == null) {
                return 0;
            }
            int leftTilt = 0;
            if (root.left != null) {
                leftTilt = findTiltDfs(root.left);
            }
            int rightTilt = 0;
            if (root.right != null) {
                rightTilt = findTiltDfs(root.right);
            }
            if (root.left == null && root.right == null) {
                return root.val;
            }
            tilt += Math.abs(leftTilt - rightTilt);
            return leftTilt + rightTilt + root.val;
        }
    }

}