/**
* 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 total = 0;
public int distributeCoins(TreeNode root) {
helper(root);
return total;
}
private int helper(TreeNode root) {
if (root == null) return 0;
int left = helper(root.left);
total += Math.abs(left);
int right = helper(root.right);
total += Math.abs(right);
return left + right + root.val - 1;
}
}