/* 
* Code example for CP264 Data Structures II
* String comparison function
* HBF 
*/
#include<stdio.h>
#include<string.h>
 
main()
{
  char a[100] = "abc";
  char b[100] = "ab";
  
  printf("use fgets to get a string from keyboard (stop at enter \\n is the last char of then string):");
  fgets(a, sizeof(a), stdin);
  printf("\n%s", a);
  printf("%d", strlen(a)); 
  a[strlen(a)-1] = '\0';	
  printf("\n%s", a);
  printf("\n%d", strlen(a));
 
  printf("\nuse scanf to get a string from keyboard (will stop at first space or enter):");
  scanf("%s", b);
  printf("%s", b);
  printf("\n%d\n", strlen(b));
  
  printf("compare(%s,%s)=%d\n", a, b, compare(a, b));
  printf("compare(%s,%s)=%d\n", b, a, compare(b, a));
  printf("compare(%s,%s)=%d\n", a, a, compare(a, a));
  
  printf("comparep(%s,%s)=%d\n", a, b, comparep(a, b));
  printf("comparep(%s,%s)=%d\n", b, a, comparep(b, a));
  printf("comparep(%s,%s)=%d\n", a, a, comparep(a, a));
   
  printf("strcmp(%s,%s)=%d\n", a, b, strcmp(a, b));
  printf("strcmp(%s,%s)=%d\n", b, a, strcmp(b, a));
  printf("strcmp(%s,%s)=%d\n", a, a, strcmp(a, a));
  
  //char *s1 = "abc";
  //char *s2 = "ab";
  
  char *s1 = &a[0];
  char *s2 = &b[0];
  
  printf("compare(%s,%s)=%d\n", s1, s2, compare(s1, s2));
  printf("compare(%s,%s)=%d\n", s2, s1, compare(s2, s1));
  printf("compare(%s,%s)=%d\n", s1, s1, compare(s1, s1));
  
  printf("comparep(%s,%s)=%d\n", s1, s2, comparep(s1, s2));
  printf("comparep(%s,%s)=%d\n", s2, s1, comparep(s2, s1));
  printf("comparep(%s,%s)=%d\n", s1, s1, comparep(s1, s1));
   
  printf("strcmp(%s,%s)=%d\n", s1, s2, strcmp(s1, s2));
  printf("strcmp(%s,%s)=%d\n", s2, s1, strcmp(s2, s1));
  printf("strcmp(%s,%s)=%d\n", s1, s1, strcmp(s1, s1));

  char *s3 = NULL;
  char *s4 = "ab";
  
  printf("%d\n", comparep(s3, s4));
  //printf("%d\n", strcmp(s3, s4)); // run time error

}

int compare(char s1[], char s2[])
{  
  int i = 0;
  while( s1[i] || s2[i] )
  {
	  if (s1[i] < s2[i]) return -1;
	  else if (s1[i] > s2[i]) return 1;
	  else {
		  i++;
	  }
  }
  return 0; 
}

int comparep(const char *s1, const char *s2)
{
  if ( s1 == NULL || s2 == NULL) return -2;  
  while (*s1 || *s2) {
	  if (*s1 < *s2) return -1;
	  else if (*s1 > *s2) return 1;
	  else {
		  s1++;
		  s2++;
	  }
  }
  return 0;  
}

/*
compare(abc,ab)=1
compare(ab,abc)=-1
compare(abc,abc)=0
comparep(abc,ab)=1
comparep(ab,abc)=-1
comparep(abc,abc)=0
strcmp(abc,ab)=1
strcmp(ab,abc)=-1
strcmp(abc,abc)=0
compare(abc,ab)=1
compare(ab,abc)=-1
compare(abc,abc)=0
comparep(abc,ab)=1
comparep(ab,abc)=-1
comparep(abc,abc)=0
strcmp(abc,ab)=1
strcmp(ab,abc)=-1
strcmp(abc,abc)=0
-2
*/