QuickSort

sorting.py

@@ -9,86 +9,40 @@ Al final se imprimen los promedios de cada algortimo
 from random import randint
 import time
 
-def merge(lista, start, middle, end):
-	# Create Temp arrays with specifically needed sizes foe the given array
-	sizeOfHalf1 = middle - start + 1
-	sizeOfHalf2 = end - middle
-	half1 = [0] * (sizeOfHalf1)
-	half2 = [0] * (sizeOfHalf2)
-    # Copy data from the received array to the temporary working arrays
-	for i in range(0, sizeOfHalf1):
-		half1[i] = lista[start + i]
-	for t in range(0,sizeOfHalf2):
-		half2[t] = lista[middle + 1 + t] 
-	
-	# Merge the temporary arrays back into the recieved list
-	i = 0 # initial index of firs subarray 
-	t = 0 # initial index of second subarray
-	k = start # initial index of merged subarray
-
-	while i < sizeOfHalf1 and t < sizeOfHalf2:
-		if half1[i] <= half2[t]:
-			lista[k] = half1[i]
-			i += 1
-		else:
-			lista[k] = half2[t]
-			t += 1
-		k += 1
-	# Copy the remaining elements on half1 if there are any
-	while i < sizeOfHalf1:
-		lista[k] = half1[i]
-		i += 1
-		k += 1
-
-	# Copy the remaining elements on half2 if there are any
-	while t < sizeOfHalf2:
-		lista[k] = half2[t]
-		t += 1
-		k += 1
-
-# start is for left index and end is the right index of the subarray
-# of lista to be stored 
-
-def mergeSort(lista,l,r):
+def mergeSort(lista):
 	#definan el algoritmo de ordenamiento mergesort
-	if l < r:
-		# Same as (l+r)//2, but avoids overflow for
-        # large l and h
-		m = l+(r-l)//2
-
-		# Sort each half
-		mergeSort(lista, l, m)
-		mergeSort(lista, m+1, r)
-		# Merge the sorted halves
-		merge(lista, l, m, r)
+	return lista
 
+def heapSort(lista):
+	#definan el algoritmo de ordenamiento heapsort
 	return lista
 
-# https://en.wikipedia.org/wiki/Heapsort
-def heapify(lista, n, i):
-	largest = i
-	l = 2 * i + 1
-	r = 2 * i + 2
-	if l < n and lista[i] < lista[l]:
-		largest = l
-	if r < n and lista[largest] < lista[r]:
-		largest = r
-	if largest != i:
-		lista[i], lista[largest] = lista[largest], lista[i]
-		heapify(lista, n, largest)
+def quickSort(lista):
+    #definan el algoritmo de ordenamiento quicksort
+    elements = len(lista)
 
-def heapSort(lista):
-	n = len(lista)
+    #Base case
+    if elements < 2:
+        return lista
 
-	for i in range(n//2, -1, -1):
-		heapify(lista, n, i)
+    current_position = 0 #Position of the partitioning element
 
-	for i in range(n-1, 0, -1):
-		lista[i], lista[0] = lista[0], lista[i]
-		heapify(lista, i, 0)
+    for i in range(1, elements): #Partitioning loop
+         if lista[i] <= lista[0]:
+              current_position += 1
+              temp = lista[i]
+              lista[i] = lista[current_position]
+              lista[current_position] = temp
 
-def quickSort(lista):
-	#definan el algoritmo de ordenamiento quicksort
+    temp = lista[0]
+    lista[0] = lista[current_position]
+    lista[current_position] = temp #Brings pivot to it's appropriate position
+
+	left = quickSort(lista[0:current_position]) #Sorts the elements to the left of pivot
+	right = quickSort(lista[current_position+1:elements]) #sorts the elements to the right of pivot
+
+	lista = left + [lista[current_position]] + right #Merging everything together
+    
 	return lista
 
 def shellSort(lista):
@@ -111,9 +65,7 @@ for i in range(veces):
 	searchlista=list(mergelista)
 
 	t1 = time.clock() 				#seteamos el tiempo al empezar
-	l = 0
-	r = len(mergelista) - 1
-	finished = mergeSort(mergelista, l,r) 				#ejecutamos el algoritmo mergeSort
+	mergeSort(mergelista) 				#ejecutamos el algoritmo mergeSort
 	acumulaMerge+=time.clock()-t1 	#acumulamos el tiempo de ejecucion
 	
 	t1 = time.clock()				#seteamos el tiempo al empezar
@@ -129,7 +81,7 @@ for i in range(veces):
 	acumulaShell+=time.clock()-t1 	#acumulamos el tiempo de ejecucion
 
 #imprimos los resultados
-print "Promedio de tiempo de ejecucion de " + str(veces) +" listas de largo " + str(largoLista)
+print "Promedio de tiempo de ejecucion de "+ str(veces) +" listas de largo " + str(largoLista)
 print "MergeSort " + str(acumulaMerge/veces) + " segundos"
 print "HeapSort " + str(acumulaHeap/veces) + " segundos"
 print "QuickSort " + str(acumulaQuick/veces) + " segundos"