From 175e97020d0eb0529bf1f7598effe475f8b11fc7 Mon Sep 17 00:00:00 2001
From: Matthew Ellison <m_ellison@ymail.com>
Date: Mon, 12 Nov 2018 11:35:01 -0500
Subject: [PATCH] Added some comments and a function for permutations

---
 Algorithms.hpp | 40 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 40 insertions(+)

diff --git a/Algorithms.hpp b/Algorithms.hpp
index 8598286..3dfd1d8 100644
--- a/Algorithms.hpp
+++ b/Algorithms.hpp
@@ -10,20 +10,29 @@
 #include <vector>
 #include <cinttypes>
 #include <algorithm>
+#include <string>
 
 namespace mee{
 
 
 //A list of functions in the file
 //Also works as a declaration
+//This is a function that returns all the primes <= goalNumber and returns a vector with those prime numbers
 template<class T>
 std::vector<T> getPrimes(T goalNumber);
+//This is a function that gets all the divisors of num and returns a vector containing the divisors
 template<class T>
 std::vector<T> getDivisors(T num);
+//This is a function that gets the sum of all elements in a vector and returns the number
 template <class T>
 T getSum(std::vector<T> numbers);
+//This is a function that searches a vecter for an element. Returns true if num is found in list
 template<class T>
 bool isFound(T num, std::vector<T> list);
+//This is a function that creates all permutations of a string and returns a vector of those permutations.
+//It is meant to have only the string passed into it from the calling function. num is used for recursion purposes
+//It can however be used with num if you want the first num characters to be stationary
+std::vector<std::string> getPermutations(std::string master, int num = 0);
 
 
 template<class T>
@@ -103,6 +112,37 @@ bool isFound(T num, std::vector<T> list){
 	return false;
 }
 
+std::vector<std::string> getPermutations(std::string master, int num){
+	std::vector<std::string> perms;
+	//Check if the number is out of bounds
+	if((num >= master.size()) || (num < 0)){
+		return perms;
+	}
+	//If this is the last possible recurse just return the current string
+	else if(num == (master.size() - 1)){
+		perms.push_back(master);
+		return perms;
+	}
+	//If there are more possible recurses, recurse with the current permutation
+	std::vector<std::string> temp;
+	temp = getPermutations(master, num + 1);
+	perms.insert(perms.end(), temp.begin(), temp.end());
+	//You need to swap the current letter with every possible letter after it
+	//The ones needed to swap before will happen automatically when the function recurses
+	for(int cnt = 1;(num + cnt) < master.size();++cnt){
+		std::swap(master[num], master[num + cnt]);
+		temp = getPermutations(master, num + 1);
+		perms.insert(perms.end(), temp.begin(), temp.end());
+		std::swap(master[num], master[num + cnt]);
+	}
+
+	//The array is not necessarily in alpha-numeric order. So if this is the full array sort it before returning
+	if(num == 0){
+		std::sort(perms.begin(), perms.end());
+	}
+	return perms;
+}
+
 
 }