水题,注意下过程中可能会爆int,因为n最大是int,过程中n*(n-1)会爆范围,所以可以开long long 解决。
下面贴题目和代码.
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
1 100
Sample Output
1 5050
代码如下:
#include <iostream>
#include <queue>
#include <string.h>
#include <string>
#include <algorithm>
#include <map>
#include <cstdio>
using namespace std;
long long int sum(long long int a)
{
return (1+a)*a/2;
}
int main()
{
long long int n;
while(cin>>n)
{
cout<<sum(n)<<endl<<endl;
}
return 0;
}