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# Path Sum

发表于 2015-01-04 更新于 2020-01-12 分类于 leetcode 阅读次数： 阅读次数： Disqus：

### problem

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.

### Analysis

using simple deep first search

### code

    /*
      Definition for binary tree
      struct TreeNode {
          int val;
          TreeNode *left;
          TreeNode *right;
          TreeNode(int x) : val(x), left(NULL), right(NULL)}
      };
     */
    class Solution {
    public:
        bool deep_first_search(TreeNode *node, int sum, int curSum)
        {
            if (node == NULL)
                return false;

            if (node->left == NULL && node->right == NULL)
                return curSum + node->val == sum;

            return deep_first_search(node->left, sum, curSum + node->val) || deep_first_search(node->right, sum, curSum + node->val);
        }

        bool hasPathSum(TreeNode *root, int sum) {
            // Start typing your C/C++ solution below
            // DO NOT write int main() function
            return deep_first_search(root, sum, 0);
        }
    };