Alphabetize String

This is a discussion on Alphabetize String within the C++ Programming forums, part of the General Programming Boards category; Hi, I was just wondering if there's a function out there that will alphabetize all of the letters in a ...

  1. #1
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    Alphabetize String

    Hi,

    I was just wondering if there's a function out there that will alphabetize all of the letters in a string. For example, if I typed in the string "I love New York" the function should change it to

    Code:
       eeiklnoorvwy
    Thanks, I just need it for a piece of my program.

  2. #2
    Captain Crash brewbuck's Avatar
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    It's a one-liner.

    Code:
    std::sort(str.begin(), str.end());
    Provided the data is in a std::string, not a C-style string. It can work on C-style strings too:

    Code:
    std::sort(str, str + strlen(str));
    Last edited by brewbuck; 11-09-2007 at 03:13 PM.

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    sorry new to c++, but would i just replace 'string' with whatever the input is, and the second 'string' with the variable for the output?

  4. #4
    Captain Crash brewbuck's Avatar
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    Quote Originally Posted by wco5002 View Post
    sorry new to c++, but would i just replace 'string' with whatever the input is, and the second 'string' with the variable for the output?
    No. It actually sorts the string in place, destroying the original. To keep the original but get a sorted version, make a copy first:

    Code:
    std::string sorted_string = str;
    std::sort(sorted_string.begin(), sorted_string.end());
    You also need to #include <algorithm> to get the std::sort function.

  5. #5
    Frequently Quite Prolix dwks's Avatar
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    str is the name of the string you want to sort. It's both the input and the output.
    Code:
    #include <iostream>
    #include <algorithm>
    #include <string>
    
    int main() {
        std::string str = "I love New York";
    
        std::cout << str << std::endl;
        std::sort(str.begin(), str.end());
        std::cout << str << std::endl;
    }
    Something like that.

    Note that that won't convert the letters to lowercase. You'll have to do that yourself if you want to -- use tolower() or toupper() from <cctype>.
    dwk

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    does it account for uppercase and lower case letter?

  7. #7
    Captain Crash brewbuck's Avatar
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    Quote Originally Posted by wco5002 View Post
    does it account for uppercase and lower case letter?
    It treats any uppercase letter as coming "before" any lowercase letter. If you want it to disregard case, you need to write a special comparator.

    Code:
    struct compare_no_case
    {
        bool operator()(char a, char b)
        {
            return tolower(a) < tolower(b);
        }
    };
    
    std::sort(str.begin(), str.end(), compare_no_case());
    Last edited by brewbuck; 11-09-2007 at 03:28 PM.

  8. #8
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    thanks for the pointers, got everything working good now

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