Compare the size of a string

// Function: Compare the string size
// If str1> str2 returns 1
// If str1 = str2, 0 is returned.
// If str1 <str2 returns-1
Char zstrncmp (unsigned char * str1, unsigned char * str2, byte num)
{
While (num! = 0)
{
If (* str1) = (* str2 ))
{
Str1 ++;
Str2 ++;
Num --;
}
Else if (* str1)> (* str2 ))
Return (1 );
Else
Return (-1 );
}
Return (0 );
}
 
 
If you simply compare the length, you can directly call a function similar to strlen () to compare it.
If the string size is compared, the ASCII code size of the character is compared. You can search the ASCII code table to find the size of each ASCII character.
During comparison, set a counter, starting from scratch, repeating until the character ending with the shortest, and comparing one digit by one,
1. If the nth ASCII value of string 1 is equal to the nth ASCII value of string 2, continue to compare the next
2. If the nth ASCII value of string 1 is greater than the nth ASCII value of string 2, the output result is: 1, indicating string 1> string 2; www.2cto.com
3. If the nth ASCII value of string 1 is less than the nth ASCII value of string 2, the output result is:-1 indicates string 1 <string 2;
4. If the ASCII code value of each digit is equal and the length is the same, the output result is: 0 indicating string 1 = string 2;
5. if String 1 is the first m bit of string 2, for example, abcd is compared with abcdef, string 1 <string 2. the reason is that, to 5th bits, the ASCII value of string 1 is 0, and the ASCII value of string 2 is 'E', that is, the decimal 101,
Of course the string is 2.
Specifically, cds and lesoqd start from the first place. 'C' and 'l' are compared, of course, 'C' <'L'. Therefore, "cds" <"lesoqd"
The commonly used ascii sequence is from small to large: 0 .. 9, A. Z, a. z.