C > Miscellaneous

Create suffix array and qsort it

Create suffix array and qsort it

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

void sortstrarr(void *array, unsigned n);
static int cmpr(const void *a, const void *b);

int main(int argc, char *argv[]) {
 char *strarr[1024];
 char *str = NULL;
 int i = 0, len = 0;

 if(argc == 2) {
  str = argv[1];
  len = strlen(str);
 } else {
  fprintf(stderr, "Usage: strsufsort STRING\n"); 
  return 1;
 }

 /* create suffix pointer array */
 for(i = 0; i < len; i++) 
  strarr[i] = &str[i];

 /* print it... */
 for(i = 0; i < len; i++)
  printf("%s\n", strarr[i]);

 /* qsort the sufx. ptr array  */
 sortstrarr(strarr, len);
 printf("--\n");

 /* again print it... */
 for(i = 0; i < len; i++)
  printf("%s\n", strarr[i]);

 return 0;
}

static int cmpr(const void *a, const void *b) { 
 return strcmp(*(char **)a, *(char **)b);
}

void sortstrarr(void *array, unsigned n) { 
 qsort(array, n, sizeof(char *), cmpr);
}