prevody-cisel-do-desitkove-soustavy.c

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#include <stdio.h>
#include <stdlib.h>
#include <string.h>//kvuli cemu? strlen()? kvuli strtol() asi ne ;-)

int do_desitkove(char cislo[], int zaklad) {
  int i, n;
  size_t len=strlen(cislo);
  int digit;
  int suma = 0;
  int an = 1;

  if (0==len) return 0;

//bile znaky na konci/zacatku neresime
  for (i=len-1; i>=0; i--, an *= zaklad) {
      digit = cislo[i];
      if (digit >= '0' && digit <= '9') {
         n = digit - '0';
       //if (n >= zaklad) ; //ERROR! nebo break?
         suma += an * n;
      }
      else {
         digit |= 0x20;//konverze VELKA->mala
         n = digit - 'a' + 10;
       //if (n >= zaklad || n > 36 || n < 0) ; //ERROR nebo konec/break
         suma += an * n;
      }
  }
  return suma;
}

#define NELEM(pole) (sizeof pole/sizeof pole[0])

int main(void) {
  struct test_s { char *cislo; int zaklad; } cisla[]={{"123",10},{"A1B",12},{"1010",2},{"ZZZ",36}};
  int i;
  for (i=0; i<NELEM(cisla); i++) {
  printf("Cislo %10s v soustave o zakladu %2d odpovida cislu %10d v desitkove soustave.\n",
          cisla[i].cislo, cisla[i].zaklad, do_desitkove(cisla[i].cislo, cisla[i].zaklad));
  }
  return EXIT_SUCCESS;
}