golang刷leetcode 二叉树（8）路径总和

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

      10
     /  \
    5   -3
   / \    \
  3   2   11
 / \   \
3  -2   1

返回 3。和等于 8 的路径有:

1.  5 -> 3
2.  5 -> 2 -> 1
3.  -3 -> 11

/**
 * Definition for a binary tree node.
 * type TreeNode struct {
 *     Val int
 *     Left *TreeNode
 *     Right *TreeNode
 * }
 */
func pathSum(root *TreeNode, sum int) int {
    count:=sumRoot(root,sum)
    if root!=nil{
        count+=pathSum(root.Left,sum)
        count+=pathSum(root.Right,sum)
    }
    return count
}

func sumRoot(root*TreeNode,sum int)int{
    if root==nil{
        return 0
    }
    if root.Val==sum{
        return 1 +sumRoot(root.Left,sum-root.Val)+sumRoot(root.Right,sum-root.Val)
    }
    return sumRoot(root.Left,sum-root.Val)+sumRoot(root.Right,sum-root.Val)
}