LeetCode 112. Path Sum简单程度-求解子问题

通过分解为子问题来求解； 1.首先我们要找和为sum的路径 2.当我们遍历了当前节点后，sum的值就变成了sum-curVal,这样问题就转化为求解子问题 3.结束条件很明显，必须是当前节点值等于当前sum值，并且当前节点是叶子节点，也就是当前节点的左右节点都为空

 * @description: 112. Path Sum
	Given the root of a binary tree and an integer targetSum, return true if the tree has a root-to-leaf path such that
	adding up all the values along the path equals targetSum.
	A leaf is a node with no children.
 * @return: 是否有一条路径节点之和等于目标值
 * @author: kami
 * @关键词：回溯
 * @date: 2021/7/5 9:26
*/
func hasPathSum(root *TreeNode, targetSum int) bool {
	if root == nil {
		return false
	}
	if root.Val == targetSum && root.Left == nil && root.Right == nil {
		return true
	}
	targetSum -= root.Val
	return hasPathSum(root.Left, targetSum) || hasPathSum(root.Right, targetSum)
}