Ex 3-3.cpp

// Exercise 3-3
// A little program to count how many times
// each distinct word appears in its input.
// Note: the program is not able to count
// words with and without capital letters
// as being the same. It will also distinguish
// words based on whether they are proceded or
// followed by interpunction. Considering the
// scope of this chapter, that is ok however.
#include<algorithm>
#include<ios>
#include<iostream>
#include<string>
#include<vector>

using std::cout;		using std::cin;
using std::endl;		using std::vector;
using std::string;		using std::sort;

int main(){
	// ask for the users name
	cout << "Please enter your first name: " ;
	string name ;
	cin >> name ;
	cout << "Hello, " << name << "!" << endl ;
	
	// ask for and read a text or list of words
	cout << endl << "Please enter a text or a list of words, "
					"followed by end-of-file: " ;
	vector<string> entered_words ;
	string x ;
	// invariant: entered_words contains all the words entered so far
	while(cin >> x) {
		entered_words.push_back(x) ;
	}
	
	// check that the user has entered some words at all
	typedef vector<string>::size_type vec_ssz ;
	vec_ssz size = entered_words.size() ;
	if (size == 0) {
		cout << endl << "Aah, come on man. At least enter some words. Try again." ;
		return 1 ;
	}
	
	// sort the words
	// after this words that are entered multiple times will be next to each other
	// we can then check if each word has been entered before by comparing it to
	// the previous word in the vector
	// since we have not learned anything yet about removing entries from vectors,
	// we will then create new vectors to write individual words and another one to
	// count occurrences
	sort(entered_words.begin(), entered_words.end()) ;
	
	// define vectors and vector sizes
	vector<string> unique_words ;
	vec_ssz unique_sz ;
	vector<int> tally ;
	typedef vector<int>::size_type vec_isz ;
	vec_isz tally_sz ;
	
	// invariant: we have analyzed count items in the vector entered_words so far
	for(vec_ssz count = 0; count != size; ++count) {
		if (count == 0) {
			unique_words.push_back(entered_words[0]) ;
			tally.push_back(1) ;
		} else if (entered_words[count] == unique_words[unique_sz - 1] ) {
			++tally[tally_sz - 1] ;
		} else {
			unique_words.push_back(entered_words[count]) ;
			tally.push_back(1) ;
		}
		
		// Compute the size of the unique_words en tally vectors
		unique_sz = unique_words.size() ;
		tally_sz = tally.size() ;
	}

	// invariant: we have written count words and their statistics to the output
	// stream so far
	
	for(int count = 0; count != unique_sz; ++count) {
		cout << unique_words[count] << ": used " << tally[count] << " time(s)" << endl ;
	}
	
	
	
	return 0 ;
}