معکوس کردن یک رشته

[کامبیز اسدزاده]

این یک مثال تقریبا کاملی است امتحانش کنید :

#include <iostream>

#include <string>





using namespace std;









void printReverse(const string& s)

{

	for (int i = s.length() - 1; i >= 0; --i) cout << s[i];

}





// the original string is reversed ...

// note: C++‎ strings are mutable ... i.e. can be modified (in place)

void reverse(string& s)

{

	int begin = 0, end = s.length() - 1;

	char tmp;

	while (begin < end) // swap begin and end ... char's

	{

		tmp = s[begin];

		s[begin++] = s[end];

		s[end--] = tmp;

	}

}





// a new local copy of a string is reversed

string getReverse(string s)

{

	int begin = 0, end = s.length() - 1;

	char tmp;

	while (begin < end) // swap begin and end ... char's

	{

		tmp = s[begin];

		s[begin++] = s[end];

		s[end--] = tmp;

	}

	return s; // returns a new copy of this reversed copy

}





int main()

{

	// 0 //

	string testStr = "abcdefghijklmnopqrstuvwxyz";

	cout << "(0) Original string: " << testStr << endl;





	// 1 //

	cout << "\n(1) After calling printReverse(testStr): ";

	printReverse(testStr);

	cout << endl;





	// 2 //

	// note: C++‎ strings are mutable ...

	reverse(testStr);

	cout << "\n(2) After calling reverse(testStr): " << testStr

		<< "\nThe original string is now reversed ..." << endl;





	// 3 //

	cout << "\n(3) After calling getReverse(testStr): " << getReverse(testStr)

		<< "\nThe new (temporary) copy is reversed ..."

		<< "\nbut the string passed in is still: " << testStr << endl;





	// 4 //

	cout << "\n(4) Or using reverse_iterator to print reversed: ";

	string::reverse_iterator rit = testStr.rbegin();

	string::reverse_iterator rit_end = testStr.rend();

	while (rit != rit_end) { cout << *rit; ++rit; }

	cout << "\nbut the string is still: " << testStr << endl;





	// 5 //

	cout << "\n(5) Or using const_reverse_iterator to print ... ";

	string::const_reverse_iterator crit = testStr.rbegin();

	string::const_reverse_iterator crit_end = testStr.rend();

	while (crit != crit_end) { cout << *crit; ++crit; }

	cout << "\nbut the string is still: " << testStr << endl;





	cout << "\nPress 'Enter' to continue ... " << flush;

	cin.get();

}