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.

Recurcive Solution:

/**
 * 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 hasPathSum(TreeNode *root, int sum) {
        if(!root) return false;
        else if(!root->left &&!root->right){
            return sum == root->val;
        }else{
            return hasPathSum(root->left, sum-root->val) || hasPathSum(root->right, sum-root->val);
        }
    }
};

BFS and DFS can also be applied here!

http://gongxuns.blogspot.com/2012/12/leetcodepath-sum.html