常用algorithm及其Python實現
阿新 • • 發佈:2018-04-22
至少 圖片 gh值 com 下標 python 兩個 append exchange
冒泡排序
def bubble_sort(li):
for i in range(len(li)-1): # i表示第幾趟
exchange = False
for j in range(len(li)-i-1): # j表示圖中的箭頭
if li[j] > li[j+1]:
li[j], li[j+1] = li[j+1], li[j]
exchange = True
if not exchange:
return
選擇排序
def select_sort(li): for i in range(len(li)-1): # 第i趟開始時 無序區:li[i:] # 找無序區最小值,保存最小值的位置 min_pos = i # min_pos保存最小值的位置 for j in range(i+1, len(li)): if li[j] < li[min_pos]: min_pos = j li[min_pos], li[i] = li[i], li[min_pos]
插入排序
def insert_sort(li): for i in range(1, len(li)): # i是摸到的牌的下標 tmp = li[i] j = i - 1 # j是手裏最後一張牌的下標 # 兩個終止條件:j小於0表示tmp是最小的 順序不要亂 while j >= 0 and li[j] > tmp: li[j+1] = li[j] j -= 1 # for j in range(i-1, -1, -1): # if li[j] > tmp: # li[j+1] = li[j] # else: # break li[j+1] = tmp
快速排序
def partition(li, left, right):
randi = random.randint(left, right)
li[randi], li[left] = li[left], li[randi]
tmp = li[left]
while left < right:
while left < right and li[right] >= tmp:
right -= 1
li[left] = li[right]
while left < right and li[left] <= tmp:
left += 1
li[right] = li[left]
li[left] = tmp
return left
def _quick_sort(li, left, right):
if left < right: # 至少兩個元素
mid = partition(li, left, right)
_quick_sort(li, left, mid - 1)
_quick_sort(li, mid + 1, right)
@cal_time
def quick_sort(li):
return _quick_sort(li, 0, len(li)-1)
li = list(range(10000, 0, -1))
quick_sort(li)
堆排序
def sift(li, low, high):
tmp = li[low]
i = low
j = 2 * i + 1
while j <= high: # 退出條件2:當前i位置是葉子結點,j位置超過了high
# j 指向更大的孩子
if j + 1 <= high and li[j+1] > li[j]:
j = j + 1 # 如果右孩子存在並且更大,j指向右孩子
if tmp < li[j]:
li[i] = li[j]
i = j
j = 2 * i + 1
else: # 退出條件1:tmp的值大於兩個孩子的值
break
li[i] = tmp
@cal_time
def heap_sort(li):
# 1. 建堆
n = len(li)
for i in range(n//2-1, -1, -1):
# i 是建堆時要調整的子樹的根的下標
sift(li, i, n-1)
# 2.挨個出數
for i in range(n-1, -1, -1): #i表示當前的high值 也表示棋子的位置
li[i], li[0] = li[0], li[i]
# 現在堆的範圍 0~i-1
sift(li, 0, i-1)
歸並排序
def merge(li, low, mid, high):
i = low
j = mid + 1
ltmp = []
while i <= mid and j <= high:
if li[i] < li[j]:
ltmp.append(li[i])
i += 1
else:
ltmp.append(li[j])
j += 1
while i <= mid:
ltmp.append(li[i])
i += 1
while j <= high:
ltmp.append(li[j])
j += 1
# for k in range(low, high+1):
# li[k] = ltmp[k-low]
li[low:high+1] = ltmp
def merge_sort(li, low, high):
if low < high:
mid = (low + high) // 2
merge_sort(li, low, mid)
merge_sort(li, mid+1, high)
merge(li, low, mid, high)
# li = list(range(10000))
# random.shuffle(li)
# merge_sort(li, 0, len(li)-1)
# print(li)
li = [10,4,6,3,8,2,5,7]
merge_sort(li, 0, len(li)-1)
總結
常用algorithm及其Python實現