Path Sum@leetcode

刷题必备书籍：Cracking the Coding Interview: 150 Programming Questions and Solutions 

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C++ 学习：The C++ Programming Language, 4th Edition
经典操作系统书籍，龙书：Operating System Concepts
创业：The Start-up of You: Adapt to the Future, Invest in Yourself, and Transform Your Career

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.

这题要注意处理sum这个参数的传递。刚开始我用了引用，这样就还得处理之前加过的点的值，有点儿麻烦。最后直接值传递就可以了。