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# 0979. Distribute Coins in Binary Tree

<https://leetcode.com/problems/distribute-coins-in-binary-tree>

## Description

You are given the `root` of a binary tree with `n` nodes where each `node` in the tree has `node.val` coins. There are `n` coins in total throughout the whole tree.

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

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

**Example 1:**

![](https://assets.leetcode.com/uploads/2019/01/18/tree1.png)

```
**Input:** root = [3,0,0]
**Output:** 2
**Explanation:** From the root of the tree, we move one coin to its left child, and one coin to its right child.
```

**Example 2:**

![](https://assets.leetcode.com/uploads/2019/01/18/tree2.png)

```
**Input:** root = [0,3,0]
**Output:** 3
**Explanation:** From the left child of the root, we move two coins to the root [taking two moves]. Then, we move one coin from the root of the tree to the right child.
```

**Example 3:**

![](https://assets.leetcode.com/uploads/2019/01/18/tree3.png)

```
**Input:** root = [1,0,2]
**Output:** 2
```

**Example 4:**

![](https://assets.leetcode.com/uploads/2019/01/18/tree4.png)

```
**Input:** root = [1,0,0,null,3]
**Output:** 4
```

**Constraints:**

* The number of nodes in the tree is `n`.
* `1 <= n <= 100`
* `0 <= Node.val <= n`
* The sum of all `Node.val` is `n`.

## ac

```java
```