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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.

 1 /** 2  * Definition for binary tree 3  * struct TreeNode { 4  *     int val; 5  *     TreeNode *left; 6  *     TreeNode *right; 7  *     TreeNode(int x) : val(x), left(NULL), right(NULL) {} 8  * }; 9  */10 class Solution {11 public:12     bool hasPathSum(TreeNode *root, int sum) {13         14         if(root == NULL)15             return false;16             17         int tempSum = 0;18         int flag = 0;19         pathSum(root, tempSum, sum, flag);20         if(flag == 1)21             return true;22         else23             return false;24     }25     26     void pathSum(TreeNode *root, int tempSum, int sum, int &flag)27     {28         if(root != NULL)29         {30             if(root->left == NULL && root->right == NULL)31             {32                 tempSum += root->val;33                 if(tempSum == sum)34                     flag = 1;35                 36                 return;37             }38         39             else40             {41                 tempSum += root->val;42                 pathSum(root->left, tempSum, sum, flag);43                 pathSum(root->right, tempSum, sum, flag);44             }45         }46     }47 };

 

Path Sum