Display only the 20 most used words[Word Frequency]

[markrezak]

ok ok i got it now right i copy it to vector and sort it..... here is the code


#include <iostream>
#include <fstream>
#include <algorithm>
#include <string>
#include <map>
#include <vector>

using namespace std;

typedef map<string,int> word_count_list;

struct val_lessthan : binary_function < pair<string,int>, pair<string,int>, bool >
{
bool operator() (const pair<string,int>& x, const pair<string,int>& y) const
{return x.second<y.second;}
}val_lt;

int main()
{
word_count_list word_count;
string filename;

// Get the filename.
cout << "Enter the file you wish to have searched:\n";
cin >> filename;

// Open file.
ifstream file(filename.c_str());

// Read in all the words.
string word;

while (file >> word){
// Remove punctuation.
int index;
while ((index = word.find_first_of(".,!?\\;-*+")) != string::npos)
word.erase(index, 1);

++word_count[word];
}

//copy pairs to vector
vector<pair<string,int> > wordvector;
copy(word_count.begin(), word_count.end(), back_inserter(wordvector));

//sort the vector by second (value) instead of key
sort(wordvector.begin(), wordvector.end(), val_lt);

for(int i=0; i<wordvector.size(); ++i)
cout << wordvector[i].first << " = " << wordvector[i].second << endl;

return 0;
}

to finish the porgram. i need to output the 20 most common or used words.... 

i try changing 
for(int i=0; i<wordvector.size(); ++i)
to for9int i=0,i<=20;i++)

but nothing happens

[markrezak]

cant get it right hhmmp

[Ancient Dragon]

This should do it

vector<pair<string,int> >::iterator it;

for(it = wordvector.begin(); it != wordvector.end(); it++)
   cout << (*it).first << " = " << (*it).second <<  "\n";

[markrezak]

i try using
vector<pair<string,int> >::iterator it;

for(it = wordvector.begin(); it != wordvector.end(); it++)
cout << (*it).first << " = " << (*it).second << "\n";
this does not limit the output to 20

am i missing something?

please teach me. this is the last problem to complete the program

just display the 20 most common words.

damn why cant i use the CODE button

[Ancient Dragon]

>>am i missing something?
Just add a counter, when it reaches 20 then stop the loop. Also, pay attention to the quantities that are displayed because the smallest ones are sorted to the top, not to the bottom. So the first 20 items in that array will be the smallest, not the largest. To fix that you will need to change the sort callback function on line 18 of your original post to use > operator instead of <.

>>damn why cant i use the CODE button
I don't use a button, just add code tags manually

[code]

// put your code here

[/code]

NEW DANIWEB FEATURE Look at the top of the Quick Edit window, next to the other buttons, and you will see [code] button. Just click it and paste your code between the two tags as I showed above.

[markrezak]

sir ancient dragon

i come up with this

#include <iostream>
#include <fstream>
#include <algorithm>
#include <string>
#include <map>
#include <vector>

using namespace std;

typedef map<string,int> word_count_list;

struct val_lessthan : binary_function < pair<string,int>, pair<string,int>, bool >
{
bool operator() (const pair<string,int>& x, const pair<string,int>& y) const
{return y.second<x.second;}
}val_lt;

int main()
{

word_count_list word_count;
string filename;

// Get the filename.
cout << "Enter the file you wish to have searched:\n";
cin >> filename;

// Open file.
ifstream file(filename.c_str());

// Read in all the words.
string word;

while (file >> word){
// Remove punctuation.
int index;
while ((index = word.find_first_of(".,!?\\;-*+")) != string::npos)
word.erase(index, 1);

++word_count[word];
}

//copy pairs to vector
vector<pair<string,int> > wordvector;
vector<pair<string,int> >::iterator it;
copy(word_count.begin(), word_count.end(), back_inserter(wordvector));

//sort the vector by second (value) instead of key
sort(wordvector.begin(), wordvector.end(), val_lt);
 int i ;
{
   for(it = wordvector.begin(),i=1; it!=wordvector.end(),i<21; ++it,++i)
cout<<i<<(*it).first << " = " << (*it).second <<  "\n";
if(i=20)
{         
               
    system("pause");
          }
}
}