436 sum of all integer numbers

sum of all integer numbers

时间限制： 1000 ms  |  内存限制： 65535 KB

难度： 0

描述

Your task is to find the sum of all integer numbers lying between 1 and N inclusive.

输入

There are multiple test cases.
The input consists of a single integer N that is not greater than 10000 by it's absolute value.

输出

Write a single integer number that is the sum of all integer numbers lying between 1 and N inclusive.

样例输入

3

样例输出

6

这个题就是求给出的数和1之前所有的整数的和，包括边界，需要注意的就是，可能是负数，所以提前判断一下，交换一下循环的上下限，然后循环累加就行了......看题一定要认真....要不然可能就坑了.....

#include<stdio.h>
int main()
{
	int n,i,s,j,a;
	while(scanf("%d",&n)!=EOF)
	{
		s=0;j=1;
		if(n<1)
		{
			j=n;n=1;
		}
		for(i=j;i<=n;i++)
		{
			s+=i;
		}
		printf("%d\n",s);
	}
	return 0;
}