leetCode: binary tree sum

題目是：有一顆二叉樹，每個節點都是0～9的一個數字，然後從根節點到葉子節點作爲一個整數，然後把所有葉子節點對應的整數相加

#include<iostream>
using namespace std;
struct TreeNode
{
    int val;
    TreeNode * left;
    TreeNode * right;
    TreeNode(int x):val(x),left(NULL),right(NULL)   { }
};
class Solution{
public:
    //-------------PreOerder Recursive----------------
    //----myabe the pre-order is the only right order---
    int sumNumbers_PreOrder_Recur(TreeNode *root){};

 };

 int sumNumbers_PreOrder_Recur(TreeNode *root,int val){
     if(root==NULL)
         return 0;
     val=val*10+root->val;
     if(root->left==NULL && root->right==NULL){
         return val;
     }
     return sumNumbers_PreOrder_Recur(root->left,val)+sumNumbers_PreOrder_Recur(root->right,val);
}

int main(){
    TreeNode a=TreeNode(1);
    TreeNode b=TreeNode(2);
    TreeNode c=TreeNode(3);
    TreeNode d=TreeNode(4);
    TreeNode e=TreeNode(5);
    a.left=&e;a.right=&b;
    b.left=&c;b.right=&d;
    e.left=NULL;e.right=NULL;d.left=NULL;d.right=NULL;e.left=NULL;e.right=NULL;

    int result=sumNumbers_PreOrder_Recur(&a,0);
    cout<<"the result is :"<<result<<endl;//the output should be 262

    return 1;
}