From 6443a56de84ba508df0687a29f3340d83c2953e5 Mon Sep 17 00:00:00 2001
From: Mattrixwv <m_ellison@ymail.com>
Date: Fri, 26 Mar 2021 13:27:47 -0400
Subject: [PATCH] Added getDivisors function

---
 Algorithms.ts     | 79 +++++++++++++++++++++++++++++++++++++++++++++++
 TestAlgorithms.ts | 19 +++++++++++-
 2 files changed, 97 insertions(+), 1 deletion(-)

diff --git a/Algorithms.ts b/Algorithms.ts
index dbe2a68..bd31fa6 100644
--- a/Algorithms.ts
+++ b/Algorithms.ts
@@ -389,6 +389,85 @@ export function getFactorsBig(goalNumber: bigint): bigint[]{
 	return factors;
 }
 
+export function getDivisors(goalNumber: number): number[]{
+	let divisors: number[] = [];
+
+	//Start by checking that the number is positive
+	if(goalNumber <= 0){
+		return divisors;
+	}
+	//If the number is 1 return just itself
+	else if(goalNumber == 1){
+		divisors.push(1);
+		return divisors;
+	}
+
+	//Start at 3 and loop through all numbers < sqrt(goalNumber) looking for a number that divides it evenly
+	let topPossibleDivisor: number = Math.ceil(Math.sqrt(goalNumber));
+	for(let possibleDivisor = 1;possibleDivisor <= topPossibleDivisor;++possibleDivisor){
+		//If you find one add it and the number it creates to the list
+		if((goalNumber % possibleDivisor) == 0){
+			divisors.push(possibleDivisor);
+			//Account for the possibility of sqrt(goalNumber) being a divisor
+			if(possibleDivisor != topPossibleDivisor){
+				divisors.push(goalNumber / possibleDivisor);
+			}
+			if(divisors[divisors.length - 1] == (possibleDivisor + 1)){
+				++possibleDivisor;
+			}
+		}
+	}
+
+	//Sort the list before returning it for neatness
+	divisors.sort((a, b) => a - b);
+	//Return the list
+	return divisors;
+}
+export function getDivisorsBig(goalNumber: bigint): bigint[]{
+	let divisors: bigint[] = [];
+
+	//Start by checking that the number is positive
+	if(goalNumber <= 0n){
+		return divisors;
+	}
+	//If the number is 1 return just itself
+	else if(goalNumber == 1n){
+		divisors.push(1n);
+		return divisors;
+	}
+
+	//Start at 3 and loop through all numbers < sqrt(goalNumber) looking for a number that divides it evenly
+	let topPossibleDivisor: bigint = sqrtBig(goalNumber);
+	for(let possibleDivisor = 1n;possibleDivisor <= topPossibleDivisor;++possibleDivisor){
+		//If you find one add it and the number it creates to the list
+		if((goalNumber % possibleDivisor) == 0n){
+			divisors.push(possibleDivisor);
+			//Account for the possibility of sqrt(goalNumber) being a divisors
+			if(possibleDivisor != topPossibleDivisor){
+				divisors.push(goalNumber / possibleDivisor);
+			}
+			if(divisors[divisors.length - 1] == (possibleDivisor + 1n)){
+				++possibleDivisor;
+			}
+		}
+	}
+
+	//Sort the list before returning it for neatness
+	divisors.sort((a, b) => {
+		if(a > b){
+			return 1;
+		}
+		else if(a < b){
+			return -1;
+		}
+		else{
+			return 0;
+		}
+	});
+	//Return the list
+	return divisors;
+}
+
 export function getSum(ary: number[]): number{
 	let sum: number = 0;
 	ary.forEach(a => sum += a);
diff --git a/TestAlgorithms.ts b/TestAlgorithms.ts
index dad1cb5..d0654bb 100644
--- a/TestAlgorithms.ts
+++ b/TestAlgorithms.ts
@@ -24,7 +24,7 @@ Copyright (C) 2021  Matthew Ellison
 import assert = require("assert");
 import { SSL_OP_SSLEAY_080_CLIENT_DH_BUG } from "constants";
 import { arrayEquals, getAllFib, getAllFibBig, getFactors, getFactorsBig, getPrimes, getPrimesBig, getNumPrimes, getNumPrimesBig,
-		sqrtBig, getSum, getSumBig, getProd, getProdBig } from "./Algorithms";
+		sqrtBig, getSum, getSumBig, getProd, getProdBig, getDivisors, getDivisorsBig } from "./Algorithms";
 
 
 function testArrayEquals(){
@@ -170,6 +170,22 @@ function testGetFactors(){
 	console.log("getFactors passed");
 }
 
+function testGetDivisors(){
+	//Test 1
+	let correctAnswer: number[] = [1, 2, 4, 5, 10, 20, 25, 50, 100];
+	let topNum: number = 100;
+	let answer: number[] = getDivisors(topNum);
+	assert.ok(arrayEquals(answer, correctAnswer), "getDivisors number failed");
+
+	//Test 2
+	let bigCorrectAnswer: bigint[] = [1n, 2n, 4n, 5n, 10n, 20n, 25n, 50n, 100n];
+	let bigTopNum: bigint = 100n;
+	let bigAnswer: bigint[] = getDivisorsBig(bigTopNum);
+	assert.ok(arrayEquals(bigAnswer, bigCorrectAnswer), "getDivisors BigInt failed");
+
+	console.log("getDivisors passed");
+}
+
 function testGetSum(){
 	//Test 1
 	let correctAnswer: number = 0;
@@ -219,5 +235,6 @@ testGetAllFib();
 testGetPrimes();
 testGetNumPrimes();
 testGetFactors();
+testGetDivisors();
 testGetSum();
 testGetProd();