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  1. #include <stdio.h>
  2.  
  3. // recの呼び出し回数
  4. int c = 0;
  5.  
  6. // a[n] = 2a[n-1] + a[n-2]
  7. // a[1] = 2, a[2] = 3
  8. int rec(int n)
  9. {
  10.     c++;
  11.  
  12.     if (n == 1)
  13.     {
  14.         return 2;
  15.     }
  16.     else if (n == 2)
  17.     {
  18.         return 3;
  19.     }
  20.     else
  21.     {
  22.         return 2 * rec(n-1) + rec(n-2);
  23.     }
  24. }
  25.  
  26. int main(void)
  27. {
  28.     int n = 4;
  29.     int a;
  30.  
  31.     a = rec(n);
  32.  
  33.     printf("数列a%dの値は%d\n", n, a);
  34.     printf("このときrecの呼び出し回数は%d\n", c);
  35.  
  36.     return 0;
  37. }
Success #stdin #stdout 0s 5328KB
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Standard input is empty
stdout
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数列a4の値は19
このときrecの呼び出し回数は5
https://ideone.com/oLvfpr
language:
C (gcc 8.3)
created:
2 days ago
visibility:
public

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