Path Sum

Path SumOct 14 '12

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. 

/**
 * Definition for binary tree
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
    bool hasPathSumInt(TreeNode *root, int sum, int currSum) {    
        if (!root)
            return false;    
        if (!root->left && !root->right)
            return currSum + root->val== sum;
        return hasPathSumInt(root->left, sum,  root->val + currSum) ||
               hasPathSumInt(root->right, sum, root->val + currSum);
    }
public:
    bool hasPathSum(TreeNode *root, int sum) {
        return hasPathSumInt(root, sum, 0);
    }
};