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back to boardDiscussion of Problem 1068. SumShow all messages Hide all messages#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
int main(int argc, char *argv[])
{
int n, tmp;
long sum;
scanf("%d", &n);
if (n > 10000 || n < -10000) {
printf("%d\n", 0);
return 0;
}
if (n == 0) {
printf("%d\n", 1);
return 0;
}
if (n > 0) { /* positive */
if (n % 2 == 0) { /* even */
sum = n * (n / 2 - 1) + n + (n / 2);
} else { /* not even */
sum = n * (n / 2) + n;
}
} else { /* negative */
if (n % 2 == 0) { /* even */
sum = n * (n / 2 + 1) - n - (n / 2) - 1;
tmp = ~sum + 1;
sum = tmp;
} else { /* not even */
sum = n * (n / 2) - n - 1;
tmp = ~sum + 1;
sum = tmp;
}
}
printf("%ld\n", sum);
return 0;
}
/* n * (n / 2) + n not even */
/* n * ((n / 2) - 1) + n + (n / 2) even */
/* n * (n / 2) - n - 1 negative not even */
/* n * ((n / 2) + 1) - n - (n / 2) - 1 negative even */ #include<stdio.h>
int main(){
int n,N,ans;
scanf("%d",&N);
if(N > 1){
n=N;
}else{
n=-1*N+2;
}
ans=(n*(N+1))/2;
printf("%d\n",ans);
return 0;
}
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