python 算法学习部分代码记录篇章1

Posted 2020-10-03

# -*- coding: utf-8 -*-
# @Date    : 2017-08-19 20:19:56
# @Author  : lileilei
‘‘‘那么算法和数据结构是什么呢，答曰兵法‘‘‘
‘‘‘a+b+c=1000 and a*a+b*b=c*c 求a,b,c‘‘‘
# import time
# start_time=time.time()
# for a in range(1000):#使用枚举法
#     for b in range(1000):
#         for c in range(1000):
#             if a+b+c==1000 and a*a+b*b==c*c:
#                 print(a,b,c)
# print(time.time()-start_time)
# import time #方法2
# start_time=time.time()
# for a in range(1000):
#     for b in range(1000):
#         c=1000-a-b
#         if a+b+c==1000 and a*a+b*b==c*c:
#             print(a,b,c)
# print(time.time()-start_time)
class Stack(object):
    """栈"""
    def __init__(self):
         self.__items = []
    def is_empty(self):
        """判断是否为空"""
        return self.__items == []
    def push(self, item):
        """加入元素"""
        self.__items.append(item)
    def pop(self):
        """弹出元素"""
        return self.__items.pop()
    def peek(self):
        """返回栈顶元素"""
        return self.__items[len(self.__items)-1]
    def size(self):
        """返回栈的大小"""
        return len(self.__items)
# if __name__ == "__main__":
#     stack = Stack()
#     stack.push("hello")
#     stack.push("world")
#     stack.push("itcast")
#     print (stack.size())
#     print (stack.peek())
#     print (stack.pop())
#     print (stack.pop())
#     print (stack.pop())
class Queue(object):
    ‘‘‘队列‘‘‘
    def __init__(self):
        self.__list=[]
    def addqueue(slef,item):
        #self.__list.append(item)
        self.__list.insert(0,item)
    def dequeue(self):
        return self.__list.pop()
    def is_empty(self):
        return self.__list==[]
    def size(self):
        return len(self.__list)
class Dqueue(object):
    ‘‘‘双端队‘‘‘
    def __init__(self):
        self.__list=[]
    def add_front(slef,item):
        self.__list.insert(0,item)
    def add_re(self,item):
        self.__list.insert(item)
    def dequeue(self):
        return self.__list.pop()
    def requeue(self):
        return self.__list.pop(0)
    def is_empty(self):
        return self.__list==[]
    def size(self):
        return len(self.__list)
def buule_sor(alist):#冒泡
    n=len(alist)
    for i in range(n-1):
        for j in range(n-1-i):
            count=0
            if alist[j]>alist[j+1]:
                alist[j],alist[j+1]=alist[j+1],alist[j]
                count+=1
        if 0==count:
            return
def select_sort(alist):#选择排序
    n=len(alist)
    for j in range(n-1):
        min=j
        for i in range(j+1,n):
            if alist[min] > alist[i]:
                min=i
        alist[j],alist[min]=alist[min],alist[j]
def insert_sort(alist):‘‘‘插入排序‘‘‘
    n=len(alist)
    for j in range(1,n):
        i=j
        while  i>0:
            if alist[i]<alist[i-1]:
                alist[i],alist[i-1]=alist[i-1],alist[i]
            i-=1
def shell_sort(alist):‘‘‘希尔排序‘‘‘
    n=len(alist)
    gap=n//2
    while gap>0:
        for j in range(gap,n):
            i=j
            while i>0:
                if alist[i]<alist[i-gap]:
                    alist[i],alist[i-gap]=alist[i-gap],alist[i]
                    i-=gap
                else:
                    break
        gap//=2
def quick_sort(alist,first,last):‘‘‘快速排序‘‘‘
    if first>=last:
        return
    mid_value=alist[first]
    low=first
    high=last
    while low<high:
        while low <high and alist[high]>=mid_value:
            high-=1
        alist[low]=alist[high]
        while low <high and alist[low]<mid_value:
            low+=1
        alist[high]=alist[low]
    alist[low]=mid_value
    quick_sort(alist,first,low-1)
    quick_sort(alist,low+1,last)
def me_sort(alist):‘‘‘归并排序‘‘‘
    n=len(alist)
    if n<=1:
        return alist
    mid=n//2
    left=me_sort(alist[:mid])
    right=me_sort(alist[mid:])
    left_point,right_porint=0,0
    result=[]
    while  left_point<len(left) and right_porint<len(right):
        if left[left_point] <right[right_porint]:
            result.append(left[left_point])
            left_point+=1
        else:
            result.append(right[right_porint])
            right_porint+=1
    result+=left[left_point:]
    result+=right[right_porint:]
    return result
def binary_search(alist,item):#二分查找 递归
    n=len(alist)
    if n>0:
        mid=n//2
        if alist[mid]==item:
            return True
        elif item<alist[mid]:
            return binary_search(alist[:mid],item)
        else:
            return binary_search(alist[mid+1:],item)
    return False
def brin_serce2(alist,item):#二分非递归
    n=len(alist)
    first=0
    lasr=n-1
    while first <=lasr:
        mid = (first + lasr) // 2
        if alist[mid]==item:
            return  True
        elif item<alist[mid]:
            lasr=mid-1
        else:
            first=mid+1
    return False
if __name__ == ‘__main__‘:
    listy=[54,67,76,23,34]
    print(brin_serce2(listy,55))