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

/*
 Sample midterm question:

Write a function to replace all spaces in a string with ‘%20’. 

*/

int main(int argc, char ** argv) {

  if (argc != 2) {
    fprintf(stderr, "Usage: encode string\n");
    exit(1);
  }

  char * str = argv[1];
  int len = strlen(str);
  int count = 0;

  for (int i = 0; i < len; i++) {
    if (str[i] == ' ') { count++; }
  }

  count *= 2;
  int newlen = len + count;
  char * newstr = (char *)malloc((newlen+1) * sizeof(str[0]));
  newstr[newlen] = '\0';
  for (int i = len-1; i >= 0; i--) {
    if (str[i] == ' ') {
      newstr[newlen - 1] = '0';
      newstr[newlen - 2] = '2';
      newstr[newlen - 3] = '%';
      newlen -= 3;
    } else {
      newstr[newlen - 1] = str[i];
      newlen -= 1;
    }
  }
  printf("Old: %s.  New: %s\n", str, newstr);

  free(newstr);
  return 0;
}