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 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.

第一种解法：递归

解法二：队列

用队列来存储各个结点，当前列子存储在队列中为 5->4->8->11->13->4->7->2->1，当前结点如果是叶子结点时判断是否满足题目要求，如果满足则返回，否则继续判断队列中的下一个结点。此题是典型的宽度优先例题。细节在代码中说明。