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

// initializes strs to a series of strings, in this case, letters a-z
int initStrs(char* strs[]);

// builds res up with 'n' randomly-selected entries from strs;
// 'entries' specifies how many entries are in 'strs'
void pickEntries(char* res, int n, char* strs[], int entries);

// frees memory allocated by entries in strs
void freeStrs(char* strs[]);

int main() {
  char* strs['z'-'a']; // an entry for each letter
  int len=initStrs(strs);
  char res[100+1]; // plus one for trailing '\0'
  pickEntries(res,100,strs,len);
  freeStrs(strs);
  printf("%s\n",res);
  return 0;
}

int initStrs(char* strs[]) {
  // initialize a string for each letter
  int i;
  for(i=0; i<'z'-'a'; i++) {
    strs[i]=malloc(sizeof(char[2]));
    strs[i][0]='a'+i; // current letter
    strs[i][1]='\0';  // null terminate for a c-style string
  }
  return 26;
}

void pickEntries(char* res, int n, char* strs[], int entries) {
  int i;
  res[0]='\0'; // initialize res to blank string
  //pick n random entries and append them to res:
  for(i=0; i<n; i++) {
    int pick=rand()%entries; // use mod to keep pick in range of letters
    strcat(res,strs[pick]);  // append pick to res
  }
}

void freeStrs(char* strs[]) {
  int i;
  for(i=0; i<'z'-'a'; i++)
    free(strs[i]);
}