https://leetcode.com/problems/path-sum/

Leetcode: 112. Path Sum

/**
 * Definition for a binary tree node.
 * type TreeNode struct {
 *     Val int
 *     Left *TreeNode
 *     Right *TreeNode
 * }
 */
func hasPathSum(root *TreeNode, targetSum int) bool {
    var helper func(root *TreeNode, sum int) bool
    helper = func(root *TreeNode, sum int) bool {
        if root == nil {
            return false
        }
        sum += root.Val
        // check sum for leaf
        if sum == targetSum && root.Left == nil && root.Right == nil {
            return true
        }
        return helper(root.Left, sum) || helper(root.Right, sum)
    }
    return helper(root, 0)
}