杭电1001

Sum Problem

Time Limit: 1000/500 MS (Java/Others)    Memory Limit: 65536/32768 K (Java/Others)
Total Submission(s): 191420    Accepted Submission(s): 45769

Problem Description

Hey, welcome to HDOJ(Hangzhou Dianzi University Online Judge).

In this problem, your task is to calculate SUM(n) = 1 + 2 + 3 + ... + n.

 

Input

The input will consist of a series of integers n, one integer per line.

 

Output

For each case, output SUM(n) in one line, followed by a blank line. You may assume the result will be in the range of 32-bit signed integer.

 

Sample Input

1100

 

Sample Output

15050
 
今天学习了递归。用递归来写了一下。
 
#include <iostream>
 
using namespace std;
 
int n;
 
int ans(int x)
{ 
    if(x == 1)
    return 1;
    else
    return x+ans(x-1);
}
 
int main()
{ 
    while(cin >> n) 
   { 
       cout << ans(n) << endl; cout << endl; 
   }  
   return 0;
}