Path Sum(LeetCode)

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题目：

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.

题目分析：

题目中给出一个二叉树和一个整数值sum。检查二叉树有没有一条路径，从根节点到叶子节点，其所有节点的和等于sum。有的话返回true，没有返回false。

思路：
暂略。

代码：

/** * Definition for binary tree * public class TreeNode { *     int val; *     TreeNode left; *     TreeNode right; *     TreeNode(int x) { val = x; } * } */public class Solution {    public boolean hasPathSum(TreeNode root, int sum) {        if (root == null){            return false;        }        if (root.left == null && root.right == null){            return (root.val == sum) ? true : false;        }        if (root.left != null){            if (hasPathSum(root.left, sum - root.val)){                return true;            }        }        return hasPathSum(root.right, sum - root.val);    }}

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