C++ Maps & Sets related queries

Question

I was trying to solve a particular problem from c++ primer book regarding maps & sets in which I have to make a map container which works as a word counter but I have to ignore punctuation & cases. For example, “example.” “example,” and “Example” should all increment the same key in the word counter.

Basic code of the map is as follows :-

map<string, size_t> word_count;
string word;

while (cin >> word)
    ++word_count[word];

for (const auto &a : word_count)
    cout <<a.first<<" occurs "<<a.second<<((a.second>1) ? " times" : " time");

So what should I add into this code so that my word counter would ignore cases & punctuation on same words?

Strip punctuation characters from your string, then convert it to upper (or lower) case for storage purposes as the key in your map — mathematician1975, Dec 31 '13 at 12:19

score 1 · Answer 1 · edited May 23 '17 at 12:11

#include <map>
#include <cstdlib>
#include <iostream>
#include <algorithm>

using std::map;
using std::cin;
using std::cout;
using std::endl;
using std::string;
using std::getline;
using std::transform;
using std::remove_if;

int main( int, char** )
{
    map< string, string::size_type > dictionary;

    string word = "";

    while ( getline( cin, word ) )
    {
        word.erase( remove_if( word.begin( ), word.end( ), ::isspace ), word.end( ) );
        word.erase( remove_if( word.begin( ), word.end( ), ::ispunct ), word.end( ) );

        transform( word.begin( ), word.end( ), word.begin( ), ::tolower );

        dictionary[ word ]++;
    }

    for ( const auto& entry : dictionary )
    {
        auto word = entry.first;
        auto count = entry.second;

        cout << "'" << word << "' total count: " << count << endl;
    }

  return EXIT_SUCCESS;  
}

Build

clang++ -stdlib=libc++ -std=c++11 -o homework homework.cpp

Resources

Alternatively you could exchange the while-loop with a for-loop to reduce the scope of the std::string word variable. — Ben Crowhurst, Dec 31 '13 at 13:20

score 0 · Answer 2 · answered Dec 31 '13 at 12:23

0

You can use tolower:

#include <algorithm>
#include <string> 

std::string str = "ExampleText"; 
std::transform(str.begin(), str.end(), str.begin(), ::tolower);

Also remove all punctuation symbols. For this you'll have to use custom algorithm.

answered Dec 31 '13 at 12:23

Maxim Makhun

2,197
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Please don't write a custom algorithm. STL is your friend. Please see answer above for full implementation details. – Ben Crowhurst Dec 31 '13 at 15:25

C++ Maps & Sets related queries

2 Answers2