Merge pull request #339 from rafu01/master

Added all permutation of a string in C++

C++/Algorithms/BackTrackingAlgorithms/AllPermutationOfString.cpp

@@ -0,0 +1,63 @@
+
+/*
+    title: all permutation of a string
+    what will it do: It will generate all permutation of a string
+    time complexity: O(n*n!) 
+    code written and tested by: https://github.com/rafu01
+    date: 10-oct-2020
+*/
+
+#include <iostream>
+#include <string>
+#include <algorithm>
+using namespace std;
+
+// 1st approach
+// the idea is to keep one part of the string fixed and swap the other parts
+void permutation(string s, int left, int right)
+{
+    // Base case
+    if (left == right)
+        cout << s << endl;
+    else
+    {
+        // swapping to create the permuation
+        for (int i = left; i <= right; i++)
+        {
+            swap(s[left], s[i]);
+            permutation(s, left + 1, right);
+            swap(s[left], s[i]);
+        }
+    }
+}
+// 2nd approach
+void permutationWithSTL(string s)
+{
+    // We first sort the string, so that it is converted to lexicographically smallest permutation
+    // ascennding order
+    sort(s.begin(), s.end());
+    // Keep printing next permutation while there next permutation exists
+    do
+    {
+        cout << s << endl;
+    } while (next_permutation(s.begin(), s.end()));
+}
+
+int main()
+{
+    string str = "ABC";
+    int n = str.size();
+    permutation(str, 0, n - 1);
+    permutationWithSTL(str);
+    return 0;
+}
+
+/*
+Recursive tree for first function. string: ABC
+		 ABC
+	 /        |       \
+      ABC	 BAC	  CBA  --> A is fixed in ABC, B is fixed BAC, C is fiex in CBA
+    /   \      /   \     /  \
+ ABC	ACB   BAC  BCA  CBA  CAB --> AB in ABC, AC in ACB, BA in BAC, BC in BCA, CB in CBA, CA in CAB are fixed
+ 
+ */