题解 | #二叉树根节点到叶子节点和为指定值的路径#

package main
import . "nc_tools"
func demo(root *TreeNode, sum int, path []int, result *[][]int) {
    if root.Left != nil {
        demo(root.Left, sum-root.Val, append(path, root.Val), result)
    }
    if root.Right != nil {
        demo(root.Right, sum-root.Val, append(path, root.Val), result)
    }
    if root.Left == nil && root.Right == nil && root.Val == sum {
        // append是引用操作，不是值传递。会导致正确答案被后面的操作修改掉。
        //*result = append(*result, append(path, sum))
        tmp := make([]int, len(path)+1)
        copy(tmp, append(path, sum))
        *result = append(*result, tmp)
    }
}

func pathSum(root *TreeNode, sum int) [][]int {
    if root == nil {
        return nil
    }
    result := make([][]int, 0)
    path := make([]int, 0)
    demo(root, sum, path, &result)
    return result
}