Permutation Sequence.txt

The set [1,2,3,…,n] contains a total of n! unique permutations.

By listing and labeling all of the permutations in order,
We get the following sequence (ie, for n = 3):

"123"
"132"
"213"
"231"
"312"
"321"
Given n and k, return the kth permutation sequence.

Note: Given n will be between 1 and 9 inclusive.

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void permute(int n, int k, int idx, int &count, string &solution, string &res, vector<bool> &isVisited)
{
	if(idx == n)
	{
		count++;
		if(count == k)
			res.assign(solution);
		return;
	}
	for(int i = 0; i < n; i++)
	{
		if(!isVisited[i])
		{
			isVisited[i] = true;
			solution.append(1, i + '1');
			permute(n, k, idx + 1, count, solution, res, isVisited);
			isVisited[i] = false;
			solution.assign(solution.substr(0, solution.size() - 1));
		}
	}
}

string getPermutation(int n, int k)
{
	if(n == 0)
		return "0";
	string solution, res;
	vector<bool> isVisited(n, false);
	int count = 0;
	permute(n, k, 0, count, solution, res, isVisited);
	return res;
}