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.
https://oj.leetcode.com/problems/path-sum/
思路：递归求解。
注意，val可能是负数。
/** * * be careful: the val might be negtive... */ public class Solution { public boolean hasPathSum(TreeNode root, int sum) { if (root == null) return false; if (sum == root.val && root.left == null && root.right == null) return true; return hasPathSum(root.left, sum - root.val) || hasPathSum(root.right, sum - root.val); } public static void main(String[] args) { TreeNode root = new TreeNode(-5); root.left = new TreeNode(4); root.left.left = new TreeNode(11); root.right = new TreeNode(8); root.right.right = new TreeNode(5); System.out.println(new Solution().hasPathSum(root, 10)); } }
[leetcode] Path Sum,布布扣,bubuko.com
原文：http://www.cnblogs.com/jdflyfly/p/3821434.html
