#include <stdio.h>
double factorial(int n) {
int i;
double mul;
mul = 1;
for(i = 1; i <= n; ++i)
mul *= i;
return mul;
}
int combinations(int n, int k) {
return factorial(n) / (factorial(k) * factorial(n - k));
}
int main(void) {
int n, k;
printf("输入总的元素个数: ");
scanf("%d", &n);
printf("输入要取出的元素个数: ");
scanf("%d", &k);
printf("C(%d,%d)=%d\n", n, k, combinations(n, k));
return 0;
}
#include <stdio.h>
#include <math.h>
int isPrime(int n);
int main(void) {
int n, i, count = 0;
scanf("%d", &n);
for(i = 2; i < n; ++i) {
if (isPrime(i) ) {
printf("%d ", i);
count++;
if(count % 5 == 0)
printf("\n");
}
}
return 0;
}
int isPrime(int n) {
int i, limit, flag = 1;
if(n <= 1)
flag = 0;
else if(n == 2)
flag = 1;
else if(n % 2 == 0)
flag = 0;
else {
limit = sqrt(n) + 1;
for(i = 3; i <= limit; i += 2) {
if(n % i == 0) {
flag = 0;
break;
}
}
}
return flag;