StringPermutations.cpp

#include <bits/stdc++.h>
using namespace std;

void printResult(char result[], int len)
{
	for (int i = 0; i < len; i++)
		printf("%c", result[i]);

	printf("\n");
}

void Permutation(char c[], int count[], char result[], int depth, int len, int cs)
{
	if (depth == len)
	{
		printResult(result, len);
		return;
	}

	for (int i = 0; i < cs; i++)
	{
		if (count[i] != 0)
		{
			result[depth] = c[i];
			count[i]--;
			Permutation(c, count, result, depth + 1, len, cs);
			count[i]++;
		}
	}
}

void StringPermutation(char exp[])
{
	int l = strlen(exp);
	map<char, int> cmap;
	for (int i = 0; exp[i]; i++)
	{
		cmap.insert(pair<char, int>(exp[i], 0));
		map<char, int> ::iterator it;

		it = cmap.find(exp[i]);
		++it->second;

		cmap.insert(pair<char, int>(exp[i], it->second));
	}
	char c[l + 1];
	int  oc[l + 1];

	int cs = 0;//no of unique characters
	map<char, int>::iterator it;

	for (it = cmap.begin(); it != cmap.end(); it++)
	{
		c[cs] = it->first;
		oc[cs] = it->second;
		cs++;
	}

	char result[l + 1];
	Permutation(c, oc, result, 0, l, cs);
}

int main()
{
	char exp[1000];
	cout << "Enter expression : ";
	cin >> exp;

	StringPermutation(exp);
	return 0;
}