Sorting string array

This is a discussion on Sorting string array within the C++ Programming forums, part of the General Programming Boards category; Originally Posted by laserlight That would result in a reverse ordered sort. I like it! You know, I have been ...

  1. #31
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    Quote Originally Posted by laserlight View Post
    That would result in a reverse ordered sort.
    I like it! You know, I have been learning more through reading this board, and posting; than I have learned from any book that I have found over the years.

    Thanks!
    Last edited by Phyxashun; 01-06-2009 at 02:14 PM.

  2. #32
    C++ Witch laserlight's Avatar
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    Eh, sorry ah, but I realised that I mixed up the order myself. I should have come up with the edge cases and tested first. A correct version that places empty strings at the end would be:
    Code:
    bool Books::operator<(const Book &obj) const
    {
        if (obj.Author.empty())
        {
            return !Author.empty();
        }
        else if (Author.empty())
        {
            return false;
        }
        return Author < obj.Author;
    }
    EDIT:
    Or slightly more succinctly:
    Code:
    bool Books::operator<(const Book &rhs) const
    {
        if (rhs.Author.empty())
        {
            return !Author.empty();
        }
        return !Author.empty() && Author < rhs.Author;
    }
    Last edited by laserlight; 01-06-2009 at 02:19 PM.
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  3. #33
    The larch
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    It appears that the test that puts zero items last needs to be a bit more complicated:

    Code:
    #include <iostream>
    #include <algorithm>
    #include <iterator>
    #include <cstdlib>
    
    class X
    {
        int n;
    public:
        X(): n(rand()%4) {}
        bool operator<(X rhv) const
        {
            if (n == 0) {
                return false;
            }
            else if (rhv.n == 0) {
                return true;
            }
    
            else {
                return n < rhv.n;
            }
        }
        friend std::ostream& operator<<(std::ostream& os, X x)
        {
            return os << x.n;
        }
    };
    
    int main()
    {
        const unsigned max = 80;
        X arr[max] = {};
        std::sort(arr, arr + max);
        std::copy(arr, arr + max, std::ostream_iterator<X>(std::cout, ""));
    }
    Edit: I see you've already noticed that...
    Last edited by anon; 01-06-2009 at 02:28 PM.
    I might be wrong.

    Thank you, anon. You sure know how to recognize different types of trees from quite a long way away.
    Quoted more than 1000 times (I hope).

  4. #34
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    I was going to also suggest that the books be a vector instead of an array. That would make the sorting easier, and the moving of the empty data to the end easier.

    Would it not?

  5. #35
    C++ Witch laserlight's Avatar
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    Quote Originally Posted by anon
    I see you've already noticed that...
    Ah, but your logic is slightly simpler. I should have tried to simplify the logic before trying to write the expression more succinctly. Consequently, we can more easily reduce the expression to:
    Code:
    bool Book::operator<(const Book& rhs) const
    {
        return !Author.empty() && (rhs.Author.empty() || Author < rhs.Author);
    }
    Quote Originally Posted by Phyxashun
    I was going to also suggest that the books be a vector instead of an array. That would make the sorting easier, and the moving of the empty data to the end easier.

    Would it not?
    It would not make the sorting simpler, but there are other advantages, like having a dynamic size and not needing to manually manage memory.
    Last edited by laserlight; 01-06-2009 at 02:49 PM. Reason: Books -> Book
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