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  1. #include <stdio.h>
  2.  
  3. int c = 0;
  4.  
  5. int rec(int n) {
  6.  
  7.     c++; 
  8.  
  9.     // ベースケース
  10.     if (n == 1) {
  11.         return 1;
  12.     } else if (n == 2) {
  13.         return 2;
  14.     } else {
  15.  
  16.         return -6 * rec(n - 1) - 9 * rec(n - 2);
  17.     }
  18. }
  19.  
  20. int main(void) {
  21.     int n = 5;
  22.  
  23.     int value = rec(n);
  24.     printf("数列a%dの値は%d\n", n, value);
  25.  
  26.     printf("このときrecの呼び出し回数は%d\n", c);
  27.  
  28.     return 0;
  29. }
  30.  
Success #stdin #stdout 0s 5324KB
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stdin
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Standard input is empty
stdout
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数列a5の値は-459
このときrecの呼び出し回数は9
https://ideone.com/uLrAcd
language:
C (gcc 8.3)
created:
17 hours ago
visibility:
public

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