各種排序演算法的Python實現

最近剛剛接觸python，python語法簡潔清晰，具有很好的易讀性，編寫的演算法可以很容易的看出其本質。故而用python編寫演算法，既可以熟悉演算法，又可以練習python，何樂而不為呢？

插入排序

def

insertsort
(lists):
for i in range(0, len(lists) - 1):
for j in range(i + 1, 0, -1):
if lists[j] < lists[i]:
lists[i], lists[j] = lists[j], lists[i]
else:
break

def

selectionsort
(lists):
for i in range(0, len(lists)):
min_number = i
for j in range(i + 1, len(lists)):
if lists[j] < lists[min_number]:
min_number = j
lists[i], lists[min_number] = lists[min_number], lists[i]# swap

def

mergesort
(lists):
if len(lists) <= 1:
return lists
num = int( len(lists)/2 )
return merge(mergesort(lists[:num]),
mergesort(lists[num:]))
defmerge
(left, right):
r, l = 0, 0
result = 
while l < len(left) and  r < len(right):
if left[l] < right[r]:
l += 1
else:
r += 1
result += right[r:]
result += left[l:]
return result

def

quicksort
(lists, p, r):
if (p < r):
q = partition(lists, p, r)
quicksort(lists, p, q - 1)
quicksort(lists, q + 1, r)
defpartition
(lists, p, r):
x = lists[r]
i = p - 1
for j in range(p, r):
if (lists[j] <= x):
i += 1
lists[i], lists[j] = lists[j], lists[i]
lists[i + 1], lists[r] = lists[r], lists[i + 1]
return i + 1

def

heapsort
(lists):
buildmaxheap(lists)
for i in range(len(lists) - 1, 0, -1):
lists[0], lists[i] = lists[i], lists[0]
maxheapify(lists, 0, i)
defbuildmaxheap
(lists):
for i in range((int)(len(lists) / 2) - 1, -1, -1):
maxheapify(lists, i, len(lists))
defmaxheapify
(lists, i, heap_size):
if2 * i + 1
< heap_size and lists[2 * i + 1] > lists[i]:
largest = 2 * i + 1
else:
largest = i
if2 * i + 2
< heap_size and lists[2 * i + 2] > lists[largest]:
largest = 2 * i + 2
if largest != i:
lists[i], lists[largest] = lists[largest], lists[i]
maxheapify(lists, largest, heap_size)

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