[作業] 請教一下

[robenten (大椎)]

我的作業出了一些問題  在此附上我的程式碼  若把reduce一段拿掉似乎就可以跑了
但是就不能約分了  可以指點一下嗎   謝謝:
#include <stdio.h>
#include <stdlib.h>

char scan_operator_fraction( int *nump , int *denomp);
int reduce_fraction( int n_answer , int d_answer);
void multiply_fractions( int n_1a , int d_1a , int n_2a , int d_2a , int *n_ansp , int *d_ansp);
void add_fractions( int n_1a , int d_1a , int n_2a , int d_2a , int *n_ansp , int *d_ansp);

int
main()
{
      int n_1 = 0 , d_1 = 1 , n_2 , d_2 ;
      char op ;
      int n_ans , d_ans ;
        int gcd ;
      char q ;

      do{

          op = scan_operator_fraction(&n_2,&d_2) ;
          switch(op){
                     case '+':
                          add_fractions( n_1 , d_1 , n_2 , d_2 , &n_ans , &d_ans);
                          break ;
                     case '-':
                          add_fractions( n_1 , d_1 , -n_2 , d_2 , &n_ans , &d_ans);
                          break ;
                     case '*':
                          multiply_fractions( n_1 , d_1 , n_2 , d_2 , &n_ans , &d_ans);
                                  break ;
                     case '/':
                          multiply_fractions( n_1 , d_1 , d_2 , n_2 , &n_ans , &d_ans);
                                break ;
                     }
          gcd = reduce_fraction( n_ans , d_ans );
                  n_ans = n_ans / gcd ;
                  d_ans = d_ans / gcd ;

                  printf("recent result is %d / %d.\n", n_ans , d_ans );
          n_1 = n_ans ;
          d_1 = d_ans ;
          }while( op != 'q' );
              printf("final result is %d / %d.\n", n_ans , d_ans );


          return(0);
          }


          char
          scan_operator_fraction( int *nump , int *denomp )
          {
          char op ,discard ;
          char sign , slash ;
          int status , error ;

          do{
              error = 0;
              printf("Enter a common fraction as -7/6.\n");
              status = scanf("%c%d%c%d",&sign,nump,&slash,denomp);
              if (status < 4){
                         error = 1 ;
                         printf("Invalid-please read directions carefully.\n");
              }else if (sign != '+' && sign != '-' && sign != '*' && sign != '/' && sign != 'q'){
                         error = 1 ;
                printf("Invalid-please enter the symbol + - * /.\n");
                }else if (slash != '/'){
                         error = 1 ;
                         printf("Invalid-by a slash(/).\n");
              }else if (*denomp <= 0){
                         error = 1 ;
                         printf("Invalid-denominator must be positive.\n");
              }
                          do{
                                  scanf("%c",&discard);
                          }while(discard != '\n');
                  }while(error);
              op = sign ;
              return(op);
              }



          void
          add_fractions( int n_1a , int d_1a , int n_2a , int d_2a , int *n_ansp , int *d_ansp)
          {
          int denom , numer , sign_factor ;
          denom = d_1a * d_2a ;
          numer = n_1a * d_2a + n_2a * d_1a ;
          if(numer * denom >= 0)
                  sign_factor = 1 ;
          else
                  sign_factor = -1 ;
          numer = sign_factor * abs(numer);
          denom = abs(denom);
          *n_ansp = numer ;
          *d_ansp = denom ;
          }

          void
          multiply_fractions( int n_1a , int d_1a , int n_2a , int d_2a , int *n_ansp , int *d_ansp)
          {
          int numer , denom , sign_factor ;

          numer = n_1a * n_2a ;
          denom = d_1a * d_2a ;
          if(numer * denom >= 0)
                   sign_factor = 1 ;
          else
          sign_factor = -1;
          numer = sign_factor * abs(numer);
          denom = abs(denom);
          *n_ansp = numer ;
          *d_ansp = denom ;
          }


          int
          reduce_fraction( int n_answer , int d_answer)
          {
          int n1 , n2 ;
          int temp ;
          int gcd ;

          if (abs(n_answer) > abs(d_answer)){
          n1 = abs(n_answer) ;
          n2 = abs(d_answer) ;
          }
          else{
          n1 = abs(d_answer) ;
          n2 = abs(n_answer) ;
          }
          do{
          while(n1 > n2){
          n1 = n1 – n2 ;}
          temp = n2 ;
          n2 = n1 ;
          n1 = temp ;
          }while( n2 != 0 );
          return( n1 ) ;
          }









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