Myujth

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;