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  1. #include <stdio.h>
  2.  
  3. /* 階乗を求める再帰関数 */
  4. int fact(int n)
  5. {
  6.     if(n == 0 || n == 1)
  7.         return 1;
  8.  
  9.     return n * fact(n - 1);
  10. }
  11.  
  12. /* 組み合わせ nCr を求める関数 */
  13. int comb(int n, int r)
  14. {
  15.     return fact(n) / (fact(r) * fact(n - r));
  16. }
  17.  
  18. int main(void)
  19. {
  20.     printf("5C2 = %d\n", comb(5, 2));
  21.     printf("6C3 = %d\n", comb(6, 3));
  22.     printf("7C4 = %d\n", comb(7, 4));
  23.  
  24.     return 0;
  25. }
  26.  
Success #stdin #stdout 0.01s 5316KB
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stdin
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Standard input is empty
stdout
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5C2 = 10
6C3 = 20
7C4 = 35
https://ideone.com/PACHet
language:
C (gcc 8.3)
created:
1 day ago
visibility:
public

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