From fd858c5249922159b5f146542544a3e109875477 Mon Sep 17 00:00:00 2001
From: Matthew Ellison <m_ellison@ymail.com>
Date: Sun, 24 Mar 2019 16:29:13 -0400
Subject: [PATCH] Added a function that gets all permutations of a string

---
 Algorithms.py     | 36 ++++++++++++++++++++++++++++++++++++
 testAlgorithms.py | 41 +++++++++++++++++++++++++++++++++--------
 2 files changed, 69 insertions(+), 8 deletions(-)

diff --git a/Algorithms.py b/Algorithms.py
index 67a9d70..0ff9444 100644
--- a/Algorithms.py
+++ b/Algorithms.py
@@ -219,3 +219,39 @@ def prod(nums: list) -> int:
 
 	#Return the product of all elements
 	return product
+
+#This is a function that creates all permutations of a string and returns a vector of those permutations.
+def getPermutations(master: str, num = 0) -> list:
+	perms = []
+	#Check if the number is out of bounds
+	if((num >= len(master)) or (num < 0)):
+		#Do nothing and return and empty list
+		perms
+	#If this is the last possible recurse just return the current string
+	elif(num == (len(master) - 1)):
+		perms.append(master)
+	#If there are more possible recurses, recurse with the current permutations
+	else:
+		temp = getPermutations(master, num + 1)
+		perms += temp
+		#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
+		cnt = 1
+		#while((num + cnt) < len(master)):
+		for cnt in range(1, len(master) - num):
+			#Swap two elements
+			master = master[0:num] + master[num + cnt] + master[num + 1 : num + cnt] + master[num] + master[num + cnt + 1:]
+			#Get the permutations after swapping two elements
+			temp = getPermutations(master, num + 1)
+			perms += temp
+			#Swap the elements back
+			master = master[0:num] + master[num + cnt] + master[num + 1 : num + cnt] + master[num] + master[num + cnt + 1:]
+			#Advance the counter
+			cnt += 1
+
+	#The array is not necessarily in alpha-numeric order. So if this is the full array sort it before returning
+	if(num == 0):
+		perms.sort()
+
+	#Return the list
+	return perms
diff --git a/testAlgorithms.py b/testAlgorithms.py
index 179d421..32f5465 100644
--- a/testAlgorithms.py
+++ b/testAlgorithms.py
@@ -189,6 +189,22 @@ def testProd():
 	if(not failed):
 		print("prod passed all tests")
 
+#This function tests the getPermutations function
+def testGetPermutations():
+	failed = False	#Holds whether a test was failed
+
+	#Test 1
+	permString = "012"
+	correctAnswer = ["012", "021", "102", "120", "201", "210"]
+	answer = Algorithms.getPermutations(permString)
+	if(answer != correctAnswer):
+		print("getPermutations failed the first test")
+		failed = True
+
+	#If the false was not triggered it must have passed all tests
+	if(not failed):
+		print("getPermutations passed all tests")
+
 #This runs all of the tests and times them if this script is implicitly called
 if __name__ == "__main__":
 	timer = Stopwatch()
@@ -233,27 +249,36 @@ if __name__ == "__main__":
 	timer.start()
 	testProd()
 	timer.stop()
-	print("testProd took " + timer.getString() + " to run")
+	print("testProd took " + timer.getString() + " to run\n")
+
+	#Test getPermutations
+	timer.start()
+	testGetPermutations()
+	timer.stop()
+	print("testGetPermutations took " + timer.getString() + " to run")
 
 """Results:
 getPrimes passed all tests
-testGetPrimes took 130.448 microseconds to run
+testGetPrimes took 429.000 microseconds to run
 
 getNumPrimes passed all tests
-testGetNumPrimes took 112.202 microseconds to run
+testGetNumPrimes took 324.100 microseconds to run
 
 getFactors passed all tests
-testGetFactors took 41.105 microseconds to run
+testGetFactors took 202.700 microseconds to run
 
 getDivisors passed all tests
-testGetDivisors took 15.416 microseconds to run
+testGetDivisors took 205.900 microseconds to run
 
 getFib passed all tests
-testGetFib took 3.185 milliseconds to run
+testGetFib took 1.738 milliseconds to run
 
 getAllFib passed all tests
-testGetAllFib took 25.959 microseconds to run
+testGetAllFib took 215.100 microseconds to run
 
 prod passed all tests
-testProd took 9.553 microseconds to run
+testProd took 207.000 microseconds to run
+
+getPermutations passed all tests
+testGetPermutations took 212.800 microseconds to run
 """