added code

added code to find the permutation of a string

permutation.cpp

@@ -0,0 +1,39 @@
+// C++ program to print all permutations with
+// duplicates allowed using rotate() in STL
+#include <bits/stdc++.h>
+using namespace std;
+
+// Function to print permutations of string str,
+// out is used to store permutations one by one
+void permute(string str, string out)
+{
+	// When size of str becomes 0, out has a
+	// permutation (length of out is n)
+	if (str.size() == 0)
+	{
+		cout << out << endl;
+		return;
+	}
+
+	// One be one move all characters at
+	// the beginning of out (or result)
+	for (int i = 0; i < str.size(); i++)
+	{
+		// Remove first character from str and
+		// add it to out
+		permute(str.substr(1), out + str[0]);
+
+		// Rotate string in a way second character
+		// moves to the beginning.
+		rotate(str.begin(), str.begin() + 1, str.end());
+	}
+}
+
+// Driver code
+int main()
+{
+	string str;
+    cin>> str;
+	permute(str, "");
+	return 0;
+}