pex14_10.cpp

数据结构C++代码,经典代码,受益多多,希望大家多多支持

#include <iostream.h>
#include <fstream.h>
#include <stdlib.h>
#include <ctype.h>
#pragma hdrstop

#include "binfile.h"
#include "merge.h"

// used for the frequency analysis
struct CharRec
{
	char key;
	int count;
};

// overload "<" by comparing count fields. used to
// sort a file of CharRec records
int operator< (const CharRec& x, const CharRec& y)
{
	return x.count < y.count;
}

// overload "<=" by comparing count fields. used to
// sort a file of CharRec records
int operator<= (const CharRec& x, const CharRec& y)
{
	return x.count <= y.count;
}

void main(void)
{
	// lcount is a file of CharRec records
	BinFile<CharRec> lcount("letcount",INOUT);
	CharRec r;
	// fin is the textfile to analyze
	ifstream fin;
	// text file name
	char fname[50], c;
	long pos;

	// initialize lcount to contain 26 records, each containing
	// a letter of the alphabet and a count of 0
	for(c = 'A';c <= 'Z';c++)
	{
		// key is c = 'A' .. 'Z', count is 0
		r.key = c;
		r.count = 0;
		// add each record at the end of the file
		lcount.Append(r);
	}

	// open the text file
	cout << "Enter the name of the file: ";
	cin >> fname;
	fin.open(fname,ios::in | ios::nocreate);
	if (!fin)
	{
		cerr << "Unable to open " << fname << endl;
		exit(1);
	}

	// read each character of the file
	while (fin.get(c))
		// for each alphabetic character,
		// translate each lowercase character
		// to upper case and update the count field
		// of the corresponding record of lcount
		if (isalpha(c))
		{
			// translate lowercase char to upper case
			if (islower(c))
				c = toupper(c);
			// filerecord to which the char belongs
			pos = c - 'A';
			// read the record from the file
			r = lcount.Read(pos);
			// update the count field of the file record
			r.count++;
			// write the modified record to the file
			lcount.Write(r,pos);
		}

	// sort lcount using the natural merge sort
	MergeSort(lcount,4);

	// go back to record 0 and read through the
	// file sequentially
	lcount.Reset();
	for(int i=0;i < 26;i++)
	{
		// read current file record and
		// display it
		lcount.Read(&r,1);
		if (r.count != 0)
			cout << r.key << ": " << r.count << endl;
	}

	// close the file and remove it from file system
	lcount.Delete();
}

/*
<File "pex14_10.dat">

Missing Mississippi
mornings.

<Run>

Enter the name of the file: pex14_10.dat
O: 1
R: 1
G: 2
P: 2
M: 3
N: 3
I: 7
S: 7
*/