任意整数从0-x累加的巧妙算法

巧妙的累加算法：

#include <stdio.h>

int cal(int x)
{
	
	if(x ==0)
		return 0;
	else
		return x+cal(x-1);
}

int main()
{   int x,a;
	while(1)
	{
	scanf("%d",&x);
	a = cal(x);
	printf("output x = %d\r\n",a);	
	}
	
	return 0;
}



result 
1
output x = 1
2
output x = 3
3
output x = 6
4
output x = 10
5
output x = 15
6
output x = 21
7
output x = 28
8
output x = 36