itshuffle.cpp

/*---------------------------------------------------------
 * Program: shuffle.cpp
 * Usage: ./shuffle
 *---------------------------------------------------------
 * Description: Prints a random permutation of the string
 * "helloworld" alongside the source string
 *_________________________________________________________
 */

/* INCLUDES */

#include <iostream>
#include <stdlib.h>


/* NAMESPACE FUNCTIONS */

// allows "free" use of string class, endl and cout from the namespace std
using std::string;
using std::cout;
using std::endl;


/* FUNCTIONS */

/*---------------------------------------------------------
 * Function: stringrand()
 * Usage: stringrand(string source, string &result)
 *---------------------------------------------------------
 * Description: Converts the empty string "result" into
 * a random permutation of the string "source" by
 * shuffling the contents of the prevous string. Source
 * remains untouched while result is modified and must 
 * be passed by reference
 *_________________________________________________________
 */

void stringrand(string source, string &result) {

	// seed rand
	srand(time(NULL));

	// stores random index
	int index;

	for (int i=0, j = source.length(); i<j; j--) {
		
		// retrieves random index
		index = rand() % j;

		// appends the random char to new string
		result += source[index];

		// remove char from source
		source.erase(index,1);
	}
}

int main () {

	string s = "helloworld";
	string random = "";
	
	// converts string random into a permutaton of the string s
	stringrand(s, random);

	// prints results and length of both strings
	cout << "Source String: " << s << endl << "New String: " << random << endl;
	cout << "Length of source: " << s.length() << endl << "Length of result: " << random.length() << endl;
	return 0;
}