演習

#include <stdio.h>

int fact(int);
int combi(int, int);

int main(void){
  int n, r;
  printf("組み合わせの総数nCrを計算します\n");
  printf("type n >>> ");
  scanf("%d",&n);
  printf("type r >>> ");
  scanf("%d",&r);
  printf("nCr=%d\n",combi(n,r));
  return 0;
}
int combi(int n, int r){
  return fact(n)/(fact(r)*fact(n-r));
}
int fact(int n){
  if(n<=1){
    return 1;
  }else{
    int i=2;
    int f=1;
    for(i; i<=n; i++){
      f*=i;
    }
    return f;
  }
}