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  1. #include <stdio.h>
  2. int c ;
  3. //a{n} = -6a{n-1} -9a{n-2}, a{1}=1, a{2}=2(再帰あり版)
  4. int rec(int n){
  5.     c++;
  6.     if(n == 1){
  7.         return 1;
  8.     }
  9.     else if(n == 2){
  10.         return 2;
  11.     }
  12.     else{
  13.         return -6*rec(n-1)-9*rec(n-2);
  14.     }
  15. }
  16. int main(void) {
  17.     int n = 4;
  18.     printf("数列a%dの値は%d\n", n, rec(n));
  19.     printf("このときrecの呼び出し回数は%d\n", c);
  20.     return 0;
  21. }
Success #stdin #stdout 0s 5320KB
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Standard input is empty
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数列a4の値は108
このときrecの呼び出し回数は5
https://ideone.com/C3cVJc
language:
C (gcc 8.3)
created:
18 hours ago
visibility:
public

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