## 题目

You are given a binary tree in which each node contains an integer value.

Find the number of paths that sum to a given value.

The path does not need to start or end at the root or a leaf, but it must go downwards (traveling only from parent nodes to child nodes).

The tree has no more than 1,000 nodes and the values are in the range -1,000,000 to 1,000,000.

**Example:**

1 | root = [10,5,-3,3,2,null,11,3,-2,null,1], sum = 8 |

## 思路

DFS.

## 代码

1 | # Definition for a binary tree node. |