数据结构与算法

import time
start_time=time.time()
for a in range(0,1001):
    for b in range(0,1001):
        c=1000-a-b
        if a**2+b**2==c**2:
            print("a,b,c:%d,%d,%d"%(a,b,c))
end_time=time.time()
print("times:%d"%(end_time-start_time))

#timeit模块
from timeit import Timer#从timeit模块中导入Timer类
def t1():
    li=[]
    for i in range(10000):
        li.append(i)
def t2():
    li=[]
    for i in range(10000):
        li+=[i]
def t3():
    [i for i in range(10000)]
def t4():
    list(range(10000))
def t5():
    li=[]
    for i in range(10000):
        li.extend([i])
timer1=Timer('t1()','from __main__ import t1')#构造对象，第一个是调用函数的名字，第二个是调用函数的条件
print("append:",timer1.timeit(1000))#使用对象的timeit方法，参数是函数跑多少次

timer2=Timer('t2()','from __main__ import t2')
print("+:",timer2.timeit(1000))

timer3=Timer('t3()','from __main__ import t3')
print("【】:",timer3.timeit(1000))

timer4=Timer('t4()','from __main__ import t4')
print("list:",timer4.timeit(1000))

timer5=Timer('t5()','from __main__ import t5')
print("extend:",timer5.timeit(1000))

#single_link_like
class Node (object):
    def __init__(self,elem):
        self.elem=elem
        self.next=None
class SingleLinkList(object):
    def __init__(self,node=None):
        self.__head=node
    def is_empty(self):
        return self.__head==None
    def length(self):
        cur=self.__head
        count=0
        while cur!=None:
            count+=1
            cur=cur.next
        return count
    def travel(self):
        cur=self.__head
        while cur!=None:
            print(cur.elem,end=" ")
            cur=cur.next 
    def add(self,item):#头插法
        node=Node(item)
        node.next=self.__head
        self.__head=node
    def append(self,item):#尾插法
        node=Node(item)
        if self.is_empty():
            self.__head=node
        else:
            cur=self.__head
            while cur.next!=None:
                cur=cur.next
            cur.next=node
    def insert(self,pos,item):
        if pos<=0:
            self.add(item)
        elif pos>(self.length()-1):
            self.append(item)
        else:  
            pre=self.__head
            count=0
            while count<(pos-1):
                count+=1
                pre=pre.next
            node=Node(item)
            node.next=pre.next
            pre.next=node
        
    def remove(self,item):
        cur=self.__head
        pre=None
        while cur!=None:
            if cur.elem==item:
                if cur==self.__head:
                    self.__head=cur.next
                else:
                    pre.next=cur.next
            else:
                pre=cur
                cur=cur.next
            break
    def search(self,item):
        cur=self.__head
        while cur!=None:
            if cur.elem==item:
                return True
            else:
                cur=cur.next
        return False
if __name__=="__main__":
    ll=SingleLinkList()
    print(ll.is_empty())
    print(ll.length())
    ll.append(1)
    ll.append(2)
    ll.append(3)
    ll.append(4)
    ll.append(5)
    ll.add(8)
    print(ll.is_empty())
    print(ll.length())
    ll.insert(4,40)
    ll.travel()

#双链表
class Node(object):
    def __init__ (self,item):
        self.elem=item
        self.next=None
        self.prev=None
class DoubleLinkList(object):
    def __init__(self,node=None):
        self.__head=None
    def is_empty(self):
        return self.__head is None

#栈stack
class Stack(object):
    def __init__(self):
        self.__list=[]
    def push(self,item):
        self.__list.append(item)
    def pop(self):
        return self.__list.pop()
    def peek(self):
        if self.__list:
            return self.__list[-1]
        else:
            return None
    def is_empty(self):
        return self.__list==[]
    def size(self):
        return len(self.__list)
if __name__=="__main__":
    s=Stack()
    s.push(1)
    s.push(2)
    s.push(3)
    s.push(4)
    print(s.pop())
    print(s.pop())
    print(s.pop())
    print(s.pop())

#队列
class Queue(object):
    def __init__(self):
        self.__list=[]
    def enqueue(self,item):#加元素
        self.__list.append(item)
    def dequeue(self):#减元素
        return self.__list.pop(0)
    def is_empty(self):
        return self.__lsit==[]
    def size(self):
        return len(self.__list)
    
if __name__=="__main__":
    s=Queue()
    s.enqueue(1)
    s.enqueue(2)
    s.enqueue(3)
    s.enqueue(4)
    print(s.dequeue())
    print(s.dequeue())
    print(s.dequeue())
    print(s.dequeue())

#双端队列
class Deque(object):
    def __init__(self):
        self.__list=[]
    def add_front(self,item):
        self.__list.insert(0,item)
    def add_rear(self,item):
        self.__list.append(item)
    def pop_front(self):
        return self.__list.pop(0)
    def pop_rear(self):
        return self.__list.pop()
    def is_empty(self):
        return self.__list==[]
    def size(self)；
    return len(self.__list)
if __name__=="__main__":
    s=Deque()
    s.enqueue(1)
    s.enqueue(2)
    s.enqueue(3)
    s.enqueue(4)
    print(s.dequeue())
    print(s.dequeue())
    print(s.dequeue())
    print(s.dequeue())

#Bubble sort
def bubble_sort(alist):
    for j in range(0,len(alist)-1):
        count=0
        for i in range(0,len(alist)-1-j):
            if alist[i]>alist[i+1]:
                alist[i],alist[i+1]=alist[i+1],alist[i]
                count+=1
        if count==0:
            return
#select sort
def select_sort(alist):
    n=len(alist)
    for j in range(0,n-1):
        min_index=j
        for i in range(j+1,n):
            if alist[min_index]>alist[i]:
                min_index=i
        alist[min_index],alist[j]=alist[j],alist[min_index]
def insert_sort(alist):
    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
            else:
                break
#希尔排序
def shell_sort(alist):
    n=len(alist)
    gap=n//2
    while gap>=1:    
        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
#快速排序
def quick_sort(alist,first,last):
    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)
#递归排序
def merge_sort(alist):
    n=len(alist)
    if n <=1:
        return alist
    mid =n//2
    left_li=merge_sort(alist[:mid])
    right_li=merge_sort(alist[mid:])
    #将两个有序子序列合并为一个新的整体
    left_pointer,right_pointer=0,0
    result=[]
    while left_pointer<len(left_li) and right_pointer<len(right_li):
        if left_li[left_pointer]<right_li[right_pointer]:
            result.append(left_li[left_pointer])
            left_pointer+=1
        else:
            result.append(right_li[right_pointer]) 
            right_pointer+=1
    result+=left_li[left_pointer:]
    result+=right_li[right_pointer:]
    return result
if __name__=="__main__":
    li=[54,26,93,17,77,31,44,55,20]
    print(li)
    #bubble_sort(li)
    #select_sort(li)
    #insert_sort(li)
    #shell_sort(li)
    #quick_sort(li,0,len(li)-1)
    li_2=merge_sort(alist)
    print(li_2)
    

#二分查找;
def binary_search(alist):