Question

我有以下程序：

#include <stdio.h>
#include <stdlib.h>
#include <math.h>

void    print_codes( void );     /* menu of codes */
double  decode_char( char code );

main() {
     char    code1, code2, code3;     /* one code per band */
     double  resistance;
     double  color1, color2, color3;  /* decoded values */

     /* Print codes and prompt for user input. */
     print_codes();
     printf( "\n\n\tEnter three codes. " );

     /* Read three character codes. */
     code1 = getchar();
     code2 = getchar();
     code3 = getchar();

     /* Decode each character code. */
     color1 = decode_char( code1 );
     color2 = decode_char( code2 );
     color3 = decode_char( code3 );

     /* Check whether codes were legal. */
     if ( color1 == -999.0  ||  color2 == -999.0  ||  color3 == -999.0 )
          printf( "\n\n\tBad code -- cannot compute resistance\n" );
     /* If codes were legal, compute and print resistance in ohms. */
     else {
          resistance = ( 10.0 * color1  +  color2 )  * pow( 10.0, color3 );
          printf( "\n\n\tResistance in ohms:\t%f\n", resistance );
     }

     return;
}

/*   This function prints a menu of color codes to guide the user in
     entering input.                                               */

void  print_codes( void ) {
   printf( "\n\n\tThe colored bands are coded as follows:\n\n\n\t" );
   printf( "COLOR\t\t\tCODE\n\t" );
   printf( "-----\t\t\t----\n\n" );
   printf( "\tBlack-------------------> B\n" );
   printf( "\tBrown-------------------> N\n" );
   printf( "\tRed---------------------> R\n" );
   printf( "\tOrange------------------> O\n" );
   printf( "\tYellow------------------> Y\n" );
   printf( "\tGreen-------------------> G\n" );
   printf( "\tBlue--------------------> E\n" );
   printf( "\tViolet------------------> V\n" );
   printf( "\tGray--------------------> A\n" );
   printf( "\tWhite-------------------> W\n" );
}

double decode_char( char code ) {

    if (code == 0.0) {
        return 'B';
    }
    else if (code == 1.0) {
        return 'N';
    }
    else if (code == 'R') {
        return 2.0;
    }
    else if (code == 'O') {
        return 3.0;
    }
    else if (code == 'Y') {
        return 4.0;
    }
    else if (code == 'G') {
        return 5.0;
    }
    else if (code == 'E') {
        return 6.0;
    }
    else if (code == 'V') {
        return 7.0;
    }
    else if (code == 'A') {
        return 8.0;
    }
    else if (code == 'W') {
        return 9.0;
    }
    else {
        return -990.0;
    }
}

这是一个简单的程序，可根据以下颜色代码计算欧姆： Color table

E.G。输入YVB会给我470欧姆。

我一直试图进行反向输出，用户可以输入欧姆并获得彩色输出。例如，如果用户输入470欧姆，他们就会得到这个：

Example image

我很难实现这一点，并想知道从哪里开始。我已经尝试过将char更改为double并切换值，但这根本不起作用。同样是的，我知道我应该使用switch语句而不是if语句，但这不是我现在的问题。

Answer 1

您可以使用mod运算符%来查找数字并将其与颜色匹配。然后在每个步骤之后将ohm除以10以获得下一个数字。例如：

int ohm = 470;
char map[11] = "BNROYGEVAW";
char color[10];
for (int i = 0; i < 10; i++)
    color[i] = 0;

for (int i = 0; i < 10; i++)
{
    int n = ohm % 10;
    color[i] = map[n];
    ohm /= 10;
    if (ohm == 0)
        break;
}

for (int i = 9; i >= 0; i--)
    if (color[i])
        printf("%c", color[i]);

Answer 2

也许是这样的：

#include <stdio.h>   // printf(), fprintf()
#include <errno.h>   // EINVAL
#include <stdlib.h>  // strtoull()
#define SUCCESS   0

/** ***********************************************************************
* Convert command-line string of resistor colors to ohms.
*/
int main(
      int I__argC,
      char *I__argV[]
      )
   {
   int rCode = SUCCESS;
   unsigned long long ohms;
   unsigned long long ohmsTotal;
   int power = 0;
   int value10s;
   int value1s;
   char *color[] = {"Black", "Brown", "Red", "Orange", "Yellow", "Green", "Blue", "Violet", "Gray", "White"};
   unsigned long long ohmsCheck;
   int powerCheck = 0;

   printf("\n");

   if(I__argC < 2)
      {
      rCode=EINVAL;
      fprintf(stderr, "Missing numeric resistor value parameter.\n");
      printf("USAGE: %s  {numeric resistor value in ohms}\n", I__argV[0]);
      goto CLEANUP;
      }

   ohmsTotal = ohms = strtoull(I__argV[1], NULL, 10);
   while(ohms > 99)
      {
      ++power;
      ohms  /= 10;
      }

   value10s = ohms / 10;
   value1s = ohms - (value10s * 10);

  ohmsCheck = (value10s * 10) + value1s;
  if(power)
     for(powerCheck = 0; powerCheck < power; ++powerCheck)
        ohmsCheck *= 10;

  if(ohmsCheck != ohmsTotal)
     {
     fprintf(stderr, "Invalid resistor ohms value[%llu].  (Perhaps you intended: %llu ?)\n", ohmsTotal, ohmsCheck);
     goto CLEANUP;
     }   

//RESULTS:

   printf("%llu Ohms = %s %s %s\n\n", ohmsTotal, color[value10s], color[value1s], color[power]);

CLEANUP:

   return(rCode);
   }

BONUS :(我的颜色版本为欧姆）

#include <stdio.h>   // printf(), fprintf()
#include <errno.h>   // EINVAL, ERANGE
#include <string.h>  // strerror()
#include <ctype.h>   // toupper()

#define SUCCESS   0

/** ***********************************************************************
* Convert a resistor color to an integer value.
*/
int ResistorColorToInteger(
      char  I__color,
      int  *_O_integer
      )
   {
   int rCode = SUCCESS;
   char *colorsIndex = "BNROYGEVAW";
   char *cp;

   cp=strchr(colorsIndex, toupper(I__color));
   if(!cp)
      {
      rCode=ERANGE;
      goto CLEANUP;
      }

//RESULTS:

   if(_O_integer)
      *_O_integer = cp - colorsIndex;

CLEANUP:

   return(rCode);
   }

/** ***********************************************************************
* Convert a string of three resistor colors to ohms.
*/
int ResistorColorsToOhms(
      const char         *I__colors,
      unsigned long long *_O_ohms
      )
   {
   int rCode = SUCCESS;
   int value10s;
   int value1s;
   int valuePower;
   unsigned long long power = 1;

   if(3 != strlen(I__colors))
      {
      rCode=EINVAL;
      goto CLEANUP;
      }

   rCode=ResistorColorToInteger(I__colors[0], &value10s);
   if(rCode)
      goto CLEANUP;

   rCode=ResistorColorToInteger(I__colors[1], &value1s);
   if(rCode)
      goto CLEANUP;

   rCode=ResistorColorToInteger(I__colors[2], &valuePower);
   if(rCode)
      goto CLEANUP;

   while(valuePower--)
      power *= 10;

//RESULTS:

   if(_O_ohms)
      *_O_ohms = ((value10s * 10) + value1s) * power;

CLEANUP:

   return(rCode);
   }

/** ***********************************************************************
* Display program help screen.
*/
int Usage(
      const char *I__programName
      )
   {
   int rCode=SUCCESS;

   printf("USAGE: %s  {3-color resister code}\n", I__programName);
   printf("Color code key:\n");
   printf( "\tBlack-------------------> B\n" );
   printf( "\tBrown-------------------> N\n" );
   printf( "\tRed---------------------> R\n" );
   printf( "\tOrange------------------> O\n" );
   printf( "\tYellow------------------> Y\n" );
   printf( "\tGreen-------------------> G\n" );
   printf( "\tBlue--------------------> E\n" );
   printf( "\tViolet------------------> V\n" );
   printf( "\tGray--------------------> A\n" );
   printf( "\tWhite-------------------> W\n" );
   printf("\n");

   return(rCode);
   }

/** ***********************************************************************
* Convert command-line string of resistor colors to ohms.
*/
int main(
      int I__argC,
      char *I__argV[]
      )
   {
   int rCode = SUCCESS;
   unsigned long long ohms;

   printf("\n");

   if(I__argC < 2)
      {
      rCode=EINVAL;
      fprintf(stderr, "Missing 3-color code parameter.\n");
      Usage(I__argV[0]);
      goto CLEANUP;
      }

   rCode=ResistorColorsToOhms(I__argV[1], &ohms);
   switch(rCode)
      {
      case SUCCESS:
         break;

      case EINVAL:
         fprintf(stderr, "ResistorColorsToOhms() reports that \"%s\" an invalid color code sequence.\n", I__argV[1]);
         Usage(I__argV[0]);
         goto CLEANUP;

      case ERANGE:
         fprintf(stderr, "ResistorColorsToOhms() reports that the sequence \"%s\" contains a non-key character.\n", I__argV[1]);
         Usage(I__argV[0]);
         goto CLEANUP;

      default:
         fprintf(stderr, "ResistorColorsToOhms() reports: [%d]%s (Something bad happened)\n", rCode, strerror(rCode));
         goto CLEANUP;
      }

//RESULTS:

   printf("\"%s\" = %llu Ohms\n", I__argV[1], (unsigned long long)ohms);

CLEANUP:

   return(rCode);
   }

电阻（欧姆）到适当的色带

2 个答案: