Count the top 10 films at the box office and save them in another file

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Today I saw a written test question , It's this ： Given a file (m.dat). It saves the box office statistics of various films . The format is as follows ：

《2012》 SONY 769.7 《 Harry Potter and the Deathly Hallows ( On )》 Warner Brothers 952.0 《 Star Wars: 》 Twentieth century fox 775.4 《 Shrek 4》 Paramount / DreamWorks 750.0 《 "Avatar" 》 Twentieth century fox 2,782.2 《 Harry Potter and the Goblet of Fire 》 Warner Brothers 895.9 《 Harry Potter and the Half-Blood Prince 》 Warner Brothers 934.0 《 The Lord of the rings 2： Twin towers 》 New line 925.3 《 Batman prequel 2： The dark knight 》 Warner Brothers 1,001.9 《 Harry Potter and the Sorcerer's Stone 》 Warner Brothers 974.7 《 Finding Nemo 》 Disney 867.9 《 Kung Fu Panda 》 Paramount / DreamWorks 631.7 《 Pirates of the Caribbean 3： The end of the world 》 Disney 961.0 《 Harry Potter and the prisoner of Azkaban 》 Warner Brothers 795.6 《E.T.》 World 792.9 《 Raiders of the lost ark 4： Crystal skeleton Kingdom 》 Paramount 786.6 《 The Lord of the rings 3： Return of the king 》 New line 1,119.1 《 Shrek 2》 DreamWorks 919.8 《 Toy Story Mania 3》 Disney 1,063.2 《 The matrix 2： regroup 》 Warner Brothers 742.1

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It is required to knock the code to count the top box office 10 In the movie . And save the statistical results into another file . Try to use it yourself C++ Achieve it , Code sharing, such as the following ：(linux Next gcc compile )

gcc compile , Two command line parameters should be passed in at run time , example ：./a.out m.dat li.dat （m.dat Is the source box office file .li.dat Before storage 10 The file of ）

#include <iostream>
#include <fstream>
#include <vector>
#include <algorithm>
using namespace std;
class Movie {
public:
	// Overload input operation 
	friend istream& operator>> (istream& is,
		Movie& movie) {
		return is >> movie.m_title >> movie.m_comp
			>> movie.m_gross;
	}
	// Overload output operation 
	friend ostream& operator<< (ostream& os,
		const Movie& movie) {
		return os << movie.m_title << ' '
			<< movie.m_comp << ' ' << movie.m_gross;
	}
	// Overload less than sign , be used for List Sort 
	bool operator< (const Movie& movie) const {
		return gross () > movie.gross ();
	}
private:
	// Read from the file string Convert to double return 
	double gross (void) const {
		string str (m_gross);
		size_t pos = 0;
		while ((pos = str.find_first_of ("$,", pos)) !=  // Remove the front of the box office "$" and ","
			string::npos)
			str.erase (pos, 1);
		return atof (str.c_str ());
	}
	string m_title;  // The movie name 
	string m_comp;	 // Company name 
	string m_gross;  // box office 
};
// Reading documents , The read results are stored in Vector<Movie>& vm
bool read (const char* file, vector<Movie>& vm) {
	ifstream ifs (file);
	if (! ifs) {
		perror (" Failed to open box office file ");
		return false;
	}
	Movie movie;
	while (ifs >> movie)  // Call overloaded >> The operator 
		vm.push_back (movie);
	ifs.close ();
	return true;
}
// Writing documents , hold vector<Movie>& vm Write data to file 
bool write (const char* file, const vector<Movie>& vm){
	ofstream ofs (file);
	if (! ofs) {
		perror (" Failed to open ranking file ");
		return false;
	}
	for (vector<Movie>::const_iterator it = vm.begin();
		it != vm.end (); ++it)
		ofs << *it << endl;  // Call overloaded << The operator 
	ofs.close ();
	return true;
}
int main (int argc, char* argv[]) {
	// Infer whether the number of command line parameters is legal 
	if (argc < 3) {
		cerr << " Usage method ：" << argv[0]
			<< " < Box office documents > < Ranking file >" << endl;
		return -1;
	}
	vector<Movie> vm;
	if (! read (argv[1], vm))
		return -1;
	sort (vm.begin (), vm.end ());  // Yes vm Order of elements in 
	if (vm.size () > 10)
		vm.resize (10);  // Before sorting 10 individual 
	if (! write (argv[2], vm))
		return -1;
	return 0;
}

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