leetcode:path-sum

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 andsum = 22,

              5             / \            4   8           /   / \          11  13  4         /  \      \        7    2      1

return true, as there exist a root-to-leaf path5->4->11->2which sum is 22.

题目大体意思：给定一棵二叉树和一个数，判断是否存在一条从根节点到任意节点的路径，其所经过的节点值之和等于给定的数。

思路：可以递归的实现，再调用其孩子节点之前，先把sum值减去该节点的值，然后再运行过程中检查sum值是否为0.

/**
 * 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&&root.val==sum){
            return true;
        }else{
            return(hasPathSum(root.left,sum-root.val)||hasPathSum(root.right,sum-root.val));
        }
        
    }
}