# Re: C++ solution for K & R(2nd Ed) Ex.6-4 - better solution needed

From:
red floyd <no.spam@here.dude>
Newsgroups:
comp.lang.c++
Date:
Sun, 30 Sep 2007 00:16:21 GMT
Message-ID:
<pVBLi.55790\$YL5.41430@newssvr29.news.prodigy.net>
Kai-Uwe Bux wrote:

Erik Wikstr?m wrote:

On 2007-09-29 13:41, subramanian100in@yahoo.com, India wrote:

As a beginner in C++, I have attempted the C++ solution for the
following:

Consider the Ex. 6-4 in K & R(ANSI C) 2nd Edition in Page 143 :

Write a program that prints the distinct words in its input sorted
into descending order of frequency of occurrence. Precede each word by
its count.

(Here I assume that we should NOT sort the words first. Instead sort
in decreasing order as per frequency.)

Following is my C++ solution which works fine. Kindly suggest better
way of doing it.

#include <iostream>
#include <vector>
#include <string>
#include <utility>
#include <algorithm>

I have not looked at your code, but for this you should only need to
include <iostream>, <string> and <map>.

Really? You are probably thinking of using

std::map< std::string, unsigned >

// comparator for *DECREASING* order
struct compare {
bool operator()(const std::pair<string, unsigned>& lhs,
const std::pair<string, unsigned& rhs) const
{
return lhs.second > rhs.second;
}
};

std::map<std::string, unsigned> words_and_freqs;

// fill map, then do this. Creates a set sorted by frequency

std::set<std::pair<std::string, unsigned> >
freqs_first(words_and_freqs.begin(), words_and_freqs.end(),
compare());

the set is sorted by the frequency in descending order.

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