Updated library layout

StringAlgorithms.ts

@@ -0,0 +1,89 @@
+//typescriptClasses/StringAlgorithms.ts
+//Matthew Ellison
+// Created: 07-13-21
+//Modified: 07-13-21
+//Algorithms for strings
+/*
+Copyright (C) 2021  Matthew Ellison
+
+	This program is free software: you can redistribute it and/or modify
+	it under the terms of the GNU Lesser General Public License as published by
+	the Free Software Foundation, either version 3 of the License, or
+	(at your option) any later version.
+
+	This program is distributed in the hope that it will be useful,
+	but WITHOUT ANY WARRANTY; without even the implied warranty of
+	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+	GNU Lesser General Public License for more details.
+
+	You should have received a copy of the GNU Lesser General Public License
+	along with this program.  If not, see <https://www.gnu.org/licenses/>.
+*/
+
+
+//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;
+}
+
+//Returns true if the string passed in is a palindrome
+export function isPalindrome(str: string): boolean{
+	let rev = str.split("").reverse().join("");
+	if(str == rev){
+		return true;
+	}
+	else{
+		return false;
+	}
+}
+
+//This function returns the number of times the character occurs in the string
+export function findNumOccurrence(str: string, ch: string){
+	let num: number = 0;	//Set the number of occurrences to 0 to start
+	//Loop through every character in the string and compare it to the character passed in
+	for(let strCh of str){
+		//If the character is the same as the one passed in increment the counter
+		if(strCh == ch){
+			++num;
+		}
+	}
+	//Return the number of times the character appeared in the string
+	return num;
+}