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.
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1 /** 2 * Definition for a binary tree node. 3 * public class TreeNode { 4 * int val; 5 * TreeNode left; 6 * TreeNode right; 7 * TreeNode(int x) { val = x; } 8 * } 9 */ 10 public class Solution { 11 public boolean hasPathSum(TreeNode root, int sum) { 12 if(root == null) return false; 13 if(root.left == null && root.right ==null && sum == root.val) 14 return true; 15 else{ 16 return hasPathSum(root.left,sum-root.val) || hasPathSum(root.right,sum-root.val); 17 } 18 } 19 }
原文：http://www.cnblogs.com/guoguolan/p/5396732.html