Leetcode学习笔记：#979. Distribute Coins in Binary Tree

Leetcode学习笔记：#861. Score After Flipping Matrix

Given the root of a binary tree with N nodes, each node in the tree has node.val coins, and there are N coins total.

In one move, we may choose two adjacent nodes and move one coin from one node to another. (The move may be from parent to child, or from child to parent.)

Return the number of moves required to make every node have exactly one coin.

实现：

int res = 0;
public int distributeCoins(TreeNode root){
	dfs(root);
	return res;
}

public int dfs(TreeNode root){
	if(root == null){
		return 0;
	}
	int left = dfs(root.left), right = dfs(root.right);
	res += Math.abs(left) + Math.abs.(right);
	return root.val + left + right -1;
}

思路：
DFS，前序遍历二叉树，返回给其父节点硬币的数目