Path Sum

描述

Given a binary tree and a sum, determine if the tree has a root-to-leaf path such that adding up all the values along the path equals the given sum.

For example:
Given the below binary tree and sum = 22,

              5
             / \
            4   8
           /   / \
          11  13  4
         /  \      \
        7    2      1


return true, as there exist a root-to-leaf path 5->4->11->2 which sum is 22.

题解

package algorithms

import (
	"github.com/ljun20160606/leetcode/algorithms"
)

/**
 * Definition for a binary tree node.
 * type TreeNode struct {
 *     Val int
 *     Left *TreeNode
 *     Right *TreeNode
 * }
 */

type TreeNode = algorithms.TreeNode

func hasPathSum(root *TreeNode, sum int) bool {
	if root == nil {
		return false
	}
	if sum == root.Val && root.Left == nil && root.Right == nil {
		return true
	}
	val := sum - root.Val
	return hasPathSum(root.Left, val) || hasPathSum(root.Right, val)
}