From 39199ed1378a0735985df7f44f5275021689ca39 Mon Sep 17 00:00:00 2001
From: Mattrixwv <m_ellison@ymail.com>
Date: Thu, 8 Apr 2021 13:20:39 -0400
Subject: [PATCH] Added function to get all permutations of a string

---
 Algorithms.ts | 42 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 42 insertions(+)

diff --git a/Algorithms.ts b/Algorithms.ts
index bd31fa6..d3625f7 100644
--- a/Algorithms.ts
+++ b/Algorithms.ts
@@ -498,3 +498,45 @@ export function getProdBig(ary: bigint[]): bigint{
 	ary.forEach(a => prod *= a);
 	return prod;
 }
+
+//This is a function that creates all permutations of a string and returns a vector of those permutations
+export function getPermutations(master: string): string[]{
+	return getPermutationsHelper(master, 0);
+}
+function getPermutationsHelper(master: string, num: number): string[]{
+	let perms: string[] = [];
+	//Check if the number is out of bounds
+	if((num >= master.length) || (num < 0)){
+		//Do nothing and return an empty array
+	}
+	//If this is the last possible recurse just return the current string
+	else if(num == (master.length - 1)){
+		perms.push(master);
+	}
+	//If there are more possible recurses, recurse with the current permutation
+	else{
+		let temp: string[] = getPermutationsHelper(master, num + 1);
+		temp.forEach(str => perms.push(str));
+		//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(let cnt = 1;(num + cnt) < master.length;++cnt){
+			master = swapString(master, num, (num + cnt));
+			temp = getPermutationsHelper(master, num + 1);
+			temp.forEach(str => perms.push(str));
+			master = swapString(master, num, (num + cnt));
+		}
+
+		//The array is not necessarily in alph-numeric order. So if this is the full array sort it before returning
+		if(num == 0){
+			perms.sort();
+		}
+	}
+
+	//Return the array that was build
+	return perms;
+}
+function swapString(str: string, first: number, second: number): string{
+	let tempStr: string = str.substr(0, first) + str[second] + str.substr(first + 1, second - first - 1) + str[first] + str.substr(second + 1);
+
+	return tempStr;
+}