Path Sum

two flavors:

//first
class Solution {
public:
    bool hasPathSum(TreeNode *root, int sum) {
    if(root==NULL)
        return false;
    if(root->left==NULL && root->right==NULL && root->val==sum)
        return true;
    return hasPathSum(root->left, sum-root->val)||hasPathSum(root->right,sum-root->val);
    }
};



//second
class Solution {
public:
    bool hasPathSum(TreeNode *root, int sum) {
        int cur=0;
        return help(root,cur,sum);
       
    }
    bool help(TreeNode*root, int &cur,int sum ){
        if(!root) return false;
        cur+=root->val;
        if(root->left==NULL&&root->right==NULL&& cur==sum)
            return true;
           
        if(root->left&&help(root->left,cur,sum))
            return true;
           
        if(root->right&&help(root->right,cur,sum))
            return true;
        cur-=root->val;   
        return false;   
    }
};