【C++ Primer Plus习题】17.5

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问题:

解答:

#include <iostream>
#include <fstream>
#include <string>
#include <set>
#include <windows.h>
using namespace std;

int main()
{
	SetConsoleOutputCP(CP_UTF8);
	
	ifstream fin_mat("mat.txt", ios_base::in);
	ifstream fin_pat("pat.txt", ios_base::in);

	string guest;
	set<string>mat_guest, pat_guest, guest_set;
	if (!fin_mat.is_open() || !fin_pat.is_open())
	{
		cout << "Error open files." << endl;
		exit(EXIT_FAILURE);
	}
	while (getline(fin_mat,guest)&&guest.size()>0)
	{
		mat_guest.insert(guest);
	}
	cout << "\nMat's friends are: \n";
	for (auto pd = mat_guest.begin(); pd != mat_guest.end(); pd++)
	{
		cout << *pd << " ";
	}
	while (getline(fin_pat,guest)&&guest.size()>0)
	{
		pat_guest.insert(guest);
	}
	cout << "\nPat's friends are: \n";
	for (auto pd = pat_guest.begin(); pd != pat_guest.end(); pd++)
	{
		cout << *pd << " ";
	}
	fin_mat.close();
	fin_pat.close();

	guest_set.insert(mat_guest.begin(), mat_guest.end());
	guest_set.insert(pat_guest.begin(), pat_guest.end());

	ofstream fout("guest.txt", ios_base::out);
	if (!fout.is_open())
	{
		cout << "Error open file." << endl;
		exit(EXIT_FAILURE);
	}

	for (auto pd = guest_set.begin(); pd != guest_set.end(); pd++)
	{
		fout << *pd << " ";
	}
	fout.close();

	ifstream fin("guest.txt", ios_base::in);
	if (!fin.is_open())
	{
		cout << "Error open file." << endl;
		exit(EXIT_FAILURE);
	}
	cout << "\nAll Guest list: \n";
	while (getline(fin,guest)&&guest.size()>0)
	{
		cout << guest << " ";
	}
	cout << endl;
	fin.close();

	return 0;
}