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: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.
1 /** 2 * Definition for a binary tree node. 3 * public class TreeNode { 4 * public int val; 5 * public TreeNode left; 6 * public TreeNode right; 7 * public TreeNode(int x) { val = x; } 8 * } 9 */ 10 public class Solution { 11 public bool HasPathSum(TreeNode root, int sum) { 12 return DFS(root, 0, sum); 13 } 14 15 private bool DFS(TreeNode node, int cur, int sum) 16 { 17 if (node == null) return false; 18 19 if (node.left == null && node.right == null) 20 { 21 return cur + node.val == sum; 22 } 23 24 return DFS(node.left, cur + node.val, sum) || DFS(node.right, cur + node.val, sum); 25 } 26 }
原文：http://www.cnblogs.com/liangmou/p/7855786.html