Leetcode 112. 路径总和

/**
 * DeFinition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x),left(NULL),right(NULL) {}
 * };
 */
class Solution {
public:
    
    bool visit(TreeNode* r,int want,int Now)
    {
        if(r==NULL) 
            return false;
        if(r->left==NULL && r->right==NULL)
        {
            //leaf
            return (Now+r->val==want);
        }
        else
        {
            return visit(r->left,want,Now+r->val) || visit(r->right,Now+r->val);
        }
    }
    
    bool hasPathSum(TreeNode* root,int sum) {
        if(root == NULL)
            return false;
        return visit(root,sum,0);
    }
};