Compare two strings returning the number of symbols in the correct position ("blacks") and the number of symbols in the wrong position ("whites"), MasterMind style

compare_strings_mastermind.c

#include <stdio.h>
#include <string.h>

// with help from http://www.eskimo.com/~scs/cclass/notes/sx13.html
int main( int argc, char *argv[] )
{
  char *hidden = argv[1];
  char *target = argv[2];
  char colors = atoi( argv[3] );
  printf( "Hidden %s target %s colors %d\n", hidden, target, colors);
  int i;
  int blacks = 0;
  int whites = 0;
  int colors_in_string_h[colors], colors_in_string_t[colors];
  for ( i = 0; i < colors; i++ ) {
    colors_in_string_h[i] =  colors_in_string_t[i] = 0;
  }
  for ( i = 0; i < strlen( hidden ); i++ ) {
    if ( hidden[i] == target[i] ) {
      blacks++;
      hidden[i] = target[i] = '.';
    } else {
      colors_in_string_h[hidden[i] - 'A']++;
      colors_in_string_t[target[i] - 'A']++;
    }
  }
  for ( i = 0; i < colors; i ++ ) {
    if ( colors_in_string_h[i] && colors_in_string_t[i] ) {
      whites += ( colors_in_string_h[i] <  colors_in_string_t[i])?
  colors_in_string_h[i]: colors_in_string_t[i];
    }
  }
  printf("Result: b %d w %d \n", blacks, whites );

}