String sort doesn't work properly - c

Question

I made this code which suppose to sort strings by some rules small letters are first from a-z and capital letters afterwards from A-Z but it doesn't work as I expected.
(I know the problem comes from the should_be_swapped function but I just don't understand why it doesn't work.)
All it has to do is change the String "DBCAdbca" to a new String "abcdABCD".
#include <stdio.h>
int should_be_swapped(char ch1,char ch2);
void swap_chars(char* ch1, char* ch2);
int sort_string(char* str);
int main()
{
char a[]="DCBAdcba";
if (sort_string(a))
{
printf("Sorted String: %s\n", a);
}
else
{
printf("The original String was already sorted.\n");
}
return 0;
}
int should_be_swapped(char ch1,char ch2)
{
if (ch1<ch2)
{
return 1;
}
if (ch1>ch2 && ch1<='z'&& ch1>='a' && ch2<='z'&&ch2>='a')
{
return 1;
}
if (ch1>ch2 && ch1<='Z'&& ch1>='A' && ch2<='Z'&&ch2>='A')
{
return 1;
}
else {
return 0;
}
}
void swap_chars(char* ch1, char* ch2)
{
char tmp;
tmp = *ch1;
*ch1 = *ch2;
*ch2 = tmp;
}
int sort_string(char* str)
{
int i,j,count=0;
for (j=0;str[j]!='\0';j++)
{
for (i=0;(str[i])!='\0';i++)
{
if (should_be_swapped(str[i],str[i+1]) )
{
swap_chars(&str[i],&str[i+1]);
count++;
}
}
}
if (count>0)
{
return 1;
}
else {
return 0;
}
}
Any suggestions?

Answer 1

This is my solution. It first checks if the values are within the offending range and fixes them, if a values is within a-z it's transformed into A-Z, and vice-versa. It then uses a single if statement to compare the new values, but the old values get swapped.
int should_be_swapped(char ch1,char ch2)
{
const char cn1 = ( ch1<='z'&& ch1>='a' ) ? ch1 - ( 'A' - 'a' ) : ch1 ;
const char c1 = ( ch1<='Z'&& ch1>='A' ) ? ch1 + ( 'A' - 'a' ) : cn1 ;
const char cn2 = ( ch2<='z'&& ch2>='a' ) ? ch2 - ( 'A' - 'a' ) : ch2 ;
const char c2 = ( ch2<='Z'&& ch2>='A' ) ? ch2 + ( 'A' - 'a' ) : cn2 ;
if( c1 > c2 )
{
return 1 ;
}
return 0 ;
}
Using this function in with your code gives the correct result: abcdABCD

Answer 2

int should_be_swapped(char ch1, char ch2)
{
if (ch1<ch2 && ch1 <= 'Z'&& ch1 >= 'A' && ch2 <= 'z'&&ch2 >= 'a')
{
return 1;
}
if (ch1>ch2 && ch1 <= 'z'&& ch1 >= 'a' && ch2 <= 'z'&&ch2 >= 'a')
{
return 1;
}
if (ch1>ch2 && ch1 <= 'Z'&& ch1 >= 'A' && ch2 <= 'Z'&&ch2 >= 'A')
{
return 1;
}
else { return 0; }
}
You weren't taking into account that CAPS have a lower ascii value than lowercase. This seems to produce the expected results.

Answer 3

Did you mean to do this?
int should_be_swapped(char ch1,char ch2){
if (ch1<='Z' && ch1>='A' && ch2<='z' && ch2>='a'){
return 1;
}else if (ch1<='z' && ch1>='a' && ch2<='Z' && ch2>='A'){
return 0;
}else if (ch1>ch2){
return 1;
}else{
return 0;
}
}

Answer 4

I'm going to assume that you can use greater than checks on char types and also assume that the issue is you're getting an answer that looks like ABCDabcd, instead of abcdABCD. With ASCII characters they're referred to by the computer as integer numbers i.e. 'a' is 97 and 'A' is 65 so when you are asking the computer is 'a' < 'A' the answer is no because it is comparing the integer values it associates with each character and not the alphabetic order of them.
Try using this table (http://www.asciitable.com/) and treating the characters as integers when comparing them.