Ndtyjky

I am using STL map in C++ for counting the frequency of words in a text file and words must be sort in lexicographic order. Input data is given as a text file. Ive already read and added them in map but i got a problem with sorting.

Example, i have { "Abc", "abc", "bag", "Boom", "great"}. When i added them in map, i got

Abc 1 Boom 1 abc 1 bag 1 great 1

but expected result is

Abc 1 abc 1 Boom 1 bag 1 great 1

#include <iostream>

#include <cstring>

#include <map>

#include <fstream>

using namespace std;

typedef map<string, int> word_count;



int main(){

    word_count wc;

    fstream f_in;

    f_in.open("test.in");

    string x;



    while( !f_in.eof()){

        f_in >> x;

        wc[x]++;

    }

    f_in.close();   

    return 0;

}

Here is my code for reading input. Any help for my problem? Thanks

The OP wants a custom sort order that's subtly different from the standard lexicographical order. A map with a custom sort order can be achieved by passing in a custom Compare (Compare is the third template parameter of map):

#include <algorithm>

#include <cctype>

#include <cstring>

#include <fstream>

#include <functional>

#include <iostream>

#include <map>

#include <vector>



using std::string;

using std::transform;

using std::map;

using std::cout;



struct Compare {

    bool operator() (const string& s0, const string& s1) const {

        // construct all lowercase versions of s0 and s1

        string str0(s0.length(),' ');

        string str1(s1.length(),' ');

        transform(s0.begin(), s0.end(), str0.begin(), tolower);

        transform(s1.begin(), s1.end(), str1.begin(), tolower);



        if  (!str0.empty() and !str1.empty() and str0.front()==str1.front()) {

            // do a standard lexicographic sort if the first character is the same

            return s0 < s1;

        }

        else {

            // otherwise, do a case-insensitive lexicographic sort using the lowercased strings

            return str0 < str1;

        }

    }

};



typedef map<string, int, Compare> word_count;



int main(){

    word_count wc;

    auto words = { "Abc", "abc", "bag", "Boom", "great"};



    for (auto word : words)

        wc[word]++;



    for(auto elem : wc)

        cout << elem.first << " " << elem.second << 'n';



    return 0;

}

This indeed produces the desired output:

Abc 1

abc 1

Boom 1

bag 1

great 1

Try out a live version of the code online

By default, the third template parameter of a map is less<key> (in this case, less<string>), which will sort strings in the standard lexicographical A-z order.

Here is a complete example with file reading included, and using the base sorting functionality of std::map.

#include <iostream>

#include <cstring>

#include <map>

#include <fstream>



typedef std::map<std::string, int> word_count;



int main(int argc, char** argv){

    if(argc < 2){

        std::cout << "Please provide a file name." << std::endl;

        return 1;

    }



    word_count wc;

    std::ifstream inputfile(argv[1]);



    if (inputfile.is_open()){

        std::string x;

        while(inputfile >> x){

            wc[x]++;

        }

        inputfile.close();

    }else {std::cout << "Program aborted: unable to open input file" << std::endl; return 1;}



    for(auto word: wc){

        std::cout << word.first << "t" << word.second << std::endl;

    }



    return 0;

}