常见排序算法-Python实现

常见排序算法-Python实现

python排序算法1.二分法
    python    32行#coding=utf-8 
def binary_search(input_array, value): 
"""Your code goes here.""" 
length = len(input_array) 
left = 0 
right = length-1 
if length == 1: 
return 0 if value == input_value[0] else -1 
else: 
mid = (left+right)/2 
while(right-left>1): 
if input_array[mid] == value: 
return mid 
elif input_array[mid] > value: 
right = mid 
mid = (left+right)/2 
else: 
left = mid 
mid = (left+right)/2 
if input_array[left] == value: 
return left 
elif input_array[right] == value: 
return right 
else: 
return -1 
 
test_list = [1,3,9,11,15,19,29] 
test_val1 = 25 
test_val2 = 15 
print (binary_search(test_list, test_val1)) 
print (binary_search(test_list, test_val2)) 
2.冒泡法
    python    60行#coding=utf-8 
 
# way=1递增排序 way=0递减排序 
def bubble_sort(array,way=1): 
length = len(array) 
 
if not length: 
print("Error!The length of array must be greater than 0.\n") 
return 'Wrong array'  
 
if way == 1: 
while length > 0: 
for i in range(length-1): 
if array[i] > array[i+1]: 
array[i],array[i+1] = array[i+1],array[i] 
length -= 1 
return array 
 
elif way == 0: 
while length > 0: 
for i in range(length-1): 
if array[i] < array[i+1]: 
array[i],array[i+1] = array[i+1],array[i] 
length -= 1 
return array 
 
# 加入排序判断标志，可提高运行效率 
# way=1递增排序 way=0递减排序 
def better_bubble_sort(array,way=1): 
is_sorted = True # 判断记录上次遍历是否进行过交换，若没有则表示不用再遍历了 
length = len(array) 
 
if not length: 
print("Error!The length of array must be greater than 0.\n") 
return 'Wrong array'  
 
if way == 1: 
while length > 0 and is_sorted: 
for i in range(length-1): 
is_sorted = False 
if array[i] > array[i+1]: 
array[i],array[i+1] = array[i+1],array[i] 
is_sorted = True 
length -= 1 
return array 
 
elif way == 0: 
while length > 0 and is_sorted: 
for i in range(length-1): 
is_sorted = False 
if array[i] < array[i+1]: 
array[i],array[i+1] = array[i+1],array[i] 
is_sorted = True 
length -= 1 
return array 
 
 
test = [21, 4, 1, 3, 9, 20, 25, 6, 21, 14]  
print(better_bubble_sort(test,1)) 
3.插入排序
    python    19行#coding=utf-8 
 
def insert_sort(array): 
length = len(array) 
flag = array[0] 
for x in range(1,length): 
# 之前的 
if array[x] < array[x-1]: 
flag = array[x] 
y = x 
while y != 0 and array[y-1] > flag : 
array[y] = array[y-1] 
y -= 1 
array[y] = flag 
return array 
 
test = [21, 4, 1, 3, 9, 20, 25, 20, 3] 
print(insert_sort(test)) 
4.归并排序
    python    31行#coding=utf-8 
 
def merge_sort(array): 
if len(array) <= 1: 
return array 
 
split_index = len(array)/2 
left = merge_sort(array[:split_index]) 
right = merge_sort(array[split_index:]) 
return merge(left,right) 
 
def merge(left,right): 
i = 0 
j = 0 
result = [] 
while i < len(left) and j < len(right): 
if left[i] <= right[j]: 
result.append(left[i]) 
i += 1 
else: 
result.append(right[j]) 
j += 1 
 
result += (left[i:]) 
result += (right[j:]) 
return result 
 
a = [1,2] 
test = [21, 4, 1, 3, 9, 20, 25]  
print(merge_sort(test)) 
5.选择排序
    python    16行#coding=utf-8 
 
def select_sort(array): 
length = len(array) 
# mini = array[0] 
for i in range(length): 
mini = array[i] 
for j in range(i,length): 
if array[j] < mini: 
mini = array[j] 
array[i],array[j] = array[j],array[i] 
return array 
 
test = [21, 4, 1, 3, 9, 20, 25, 20, 3]  
print(select_sort(test)) 
6.快速排序
    python    26行#coding=utf-8 
 
# 递归 
def quick_sort(lists, left, right): 
# 快速排序 
if left >= right: 
return lists 
key = lists[left] 
low = left 
high = right 
while left < right: 
while left < right and lists[right] >= key: 
right -= 1 
lists[left] = lists[right] 
while left < right and lists[left] <= key: 
left += 1 
lists[right] = lists[left] 
lists[right] = key 
quick_sort(lists, low, left - 1) 
quick_sort(lists, left + 1, high) 
return lists 
 
 
test = [21, 4, 1, 3, 9, 20, 25, 6, 21, 14] 
print (quick_sort(test,0,len(test)-1)) 

written by MARSGGBO[/b] 
2017-2-14