Question

用C语言编一程序 -1+2-3+4-5+6-7+8-9+10

Answer 1

/*

sum = 5

Press any key to continue

*/

#include <stdio.h>

int main() {
	int i,sign = -1,sum = 0;
	for(i = 1; i <= 10; ++i) {
		sum += sign * i;
		sign *= -1;
	}
	printf("sum = %d\n",sum);
	return 0;
}

Answer 2

#include"stdio.h"
main()
{
int i=1, sum=0;
while(i<=10)
{
if( i %2)
sum-=i;
else
sum+=i;
}
}

Answer 3

#include <stdio.h>
int main(void)
{
int i,k,sum=0;
for (i=1,k=-1;i<=10;sum+=k*i,k*=-1,++i);
printf("%d",sum);
return(0);
}