75.Path Sum

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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.

备注:本题目写于2015-10-19.当时忘记写博客,今天给补上。

public class Solution {

   int flag=0;public boolean hasPathSum(TreeNode root, int sum) {if(root == null ){return false; } else{ if(root.val==sum && root.left==null && root.right == null){ return true; }return hasPathSum(root.left,sum-root.val)||hasPathSum(root.right,sum-root.val); }   }}

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