Strings C++

[igoreshka3333]

Hi. I've got next problem. There was an exercise:
I must write a function void to_lower( char* s ) for replace all capitall letters with small letters in the sentence. For example: "Hello, world" to "hello world".
I can't use standart library functions.

There is my attempt:

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

int main()
{
    char* s;

    std::cout << "Enter a string: ";
    std::cin >> s;
    
    char Alphabet[26];
    int j = 0;


    for( char i = 'a'; i < 'z'; i++ ){
        Alphabet[j++] = i;
    }

    for( size_t n = 0; n < strlen( s ); n++ ){
        for( char i = 'a'; i < 'z'; i++ ){
            if( s[n] != i ){
                int count = 0;
                for( char j = 'A'; j < 'Z'; j++ ){
                    count++;
                    if( s[n] == j )
                        s[n] = Alphabet[count];
                }
                count = 0;
            }
        }
    }

    std::cout << "\nRes: " << s << std::endl;
}

The program exited without any visible errors.

[ajh32]

If you remember that the difference between the uppercase ASCII char and lowercase ASCII char is 32, i.e. a-A == 32, then you can simplify your code to:

#include<iostream>
#include <string>

int main()
{
	std::string s;

	std::cout << "Enter a string: ";
	std::getline(std::cin, s);
    
	for (int n = 0; n < s.length(); ++n)
	{
		if (s[n] >= 'A' && s[n] <= 'Z')
			s[n] += 32;
	}

	std::cout << "\nRes: " << s << std::endl;

	return 0;
}

[Peter87]

s is uninitialized.

[igoreshka3333]

Thanks!

[andywestken]

Note it is better to code it as

#include<iostream>
#include <string>

const int offset = 'a' - 'A';

int main()
{
	std::string s;

	std::cout << "Enter a string: ";
	std::getline(std::cin, s);
    
	for (int n = 0; n < s.length(); ++n)
	{
		if (s[n] >= 'A' && s[n] <= 'Z')
			s[n] += offset ;
	}

	std::cout << "\nRes: " << s << std::endl;

	return 0;
}

Rather than use the "magic number" 32. Let the compiler do the work!

Andy