Re: multimap help

From: Mike Wahler (mkwahler_at_mkwahler.net)
Date: 11/27/04 

Date: Sat, 27 Nov 2004 19:22:00 GMT

"iwasinnihon" <iwasinnihon@hotmail.com> wrote in message
news:41a7f626$0$19042$3a2ecee9@news.csolutions.net...
> I was wondering if anyone new or had example code that uses a multimap (or
> just a map). I have been looking for some and haven't really been
> successful. If anyone knows where I can find one if you'd let me know I'd
> appreciate it.
>
> Thanks

Using a std::map to store counts of occurrences of
each character value in a string:

#include <iomanip>
#include <iostream>
#include <map>
#include <ostream>
#include <string>

void tally(std::map<char, std::string::size_type>&m, const std::string& s)
{
    m.clear();
    std::string::size_type i(0);
    std::string::size_type sz(s.size());

    for(i = 0; i < sz; ++i)
        ++m[s[i]];
}

void show(std::ostream& os, const std::map<char, std::string::size_type>& m)
{
    os << "char count\n";

    std::map<char, std::string::size_type>::const_iterator it(m.begin());
    std::map<char, std::string::size_type>::const_iterator en(m.end());

    while(it != en)
    {
        os << " " << it->first << " " << std::setw(5) << it->second <<
'\n';
        ++it;
    }
}

int main()
{
    std::string s("This is a string of characters");
    std::map<char, std::string::size_type> counts;

    std::cout << "string:\n" << s << "\n\n";
    tally(counts, s);
    show(std::cout, counts);

    return 0;
}

Output:

string:
This is a string of characters

char count
          5
  T 1
  a 3
  c 2
  e 1
  f 1
  g 1
  h 2
  i 3
  n 1
  o 1
  r 3
  s 4
  t 2

Book recommendation for C++ standard library:
www.josuttis.com/libbook

-Mike

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