hledani-podretezce-zprava.c

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

static size_t up1_strlen (const char *s) {
  size_t len = 0;
  while (*s++) len++;
  return len;
}

//extern char *strstr();

char *strrstr (const char *kupka, const char *jehla) {
  char *pch2, *pk, *pj;
  if (!*jehla) return kupka;//nebo jehla?
  pch2 = kupka + up1_strlen(kupka) - up1_strlen(jehla);

  while (pch2 >= kupka) {
    pk = pch2, pj = jehla;
    while (*pj && *pj++ == *pk++)
      ;
    if (!*pj) return pch2;//jehla na konci
    pch2--;
  }
  return NULL;
}

#define STRRSTR(haystack, needle)\
  printf("Text: \"%s\"\nHledame: \"%s\"\nVraceny ukazatel: \"%s\"\n", (haystack),(needle),strrstr((haystack),(needle)))

int main(int argc, char *argv[]) {
  STRRSTR("Ahoj svete!", "svet");
  STRRSTR("Ahoj svete v jedne vete!", "vete");
  STRRSTR("kupka zadna jehla", "");//co vracet?
  STRRSTR("", "jehla zadna kupka");
  return EXIT_SUCCESS;
}