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Algorithms.py

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+#Python/myClasses/Algorithms.py
+#Matthew Ellison
+# Created: 1-27-19
+#Modified: 1-27-19
+#This is a file that contains a few algorithms that I have used several times
+
+import math
+
+#This function returns a list with all the prime numbers <= goalNumber
+def getPrimes(goalNumber: int):
+	primes = []
+	foundFactor = False
+
+	#If the number is 0 or negative return an empty list
+	if(goalNumber <= 1):
+		return primes
+	
+	#If the number is even 2 is a factor and all other factors will be odd
+	if((goalNumber %2) == 0):
+		primes.append(2)
+	#We can now start at 3 and skip all even numbers, because they cannot be prime
+	for possiblePrime in range(3, goalNumber + 1, 2): #Need goalNumber + 1 to account for goalNumber being prime
+		#See if the current possible prime is divisible by any prime less than it. If not it is a prime itself
+		for primeNum in primes:
+			if((possiblePrime % primeNum) == 0):
+				foundFactor = True
+				break
+	
+		#If you didn't find a factor then the current number must be prime
+		if(not foundFactor):
+			primes.append(possiblePrime)
+		else:
+			foundFactor = False
+
+	primes.sort()
+	return primes
+
+#This is a function that returns all the factors of goalNumber
+def getFactors(goalNumber: int):
+	#You need to get all the primes up to this number
+	primes = getPrimes(math.ceil(math.sqrt(goalNumber)))	#If there is a prime it must be <= sqrt(num)
+	factors = []
+
+	#If you didn't get any primes the number itself must be a prime
+	factors.append(goalNumber)
+	#You need to step through each prime and see if it is a factor in the number
+	cnt = 0
+	while((cnt < len(primes)) and (goalNumber > 1)):
+		#If the prime is a factor you need to add it to the factor list
+		if((goalNumber % primes[cnt]) == 0):
+			factors.append(primes[cnt])
+			goalNumber /= primes[cnt]
+		#Otherwise advance the location in primes you are looking at
+		#By not advancing if the prime is a factor you allow for multiple of the same prime number as a factor
+		else:
+			cnt += 1
+
+	#If for some reason the goalNumber is not 0 print an error message
+	if(goalNumber > 1):
+		print("There was an error in getFactors(). A leftover of " + str(goalNumber))
+	
+	#Return the list of factors
+	return factors