python简单算法整理

冒泡排序

def func(alist):
    for x in range(1,len(alist)):
        for i in range(0,len(alist)-x):
            if alist[i] > alist[i+1]:
                alist[i], alist[i+1] = alist[i+1], alist[i]
    return alist
print(func([1,4,2,3,6,7,8,9,0,5]))

选择排序

def func(alist):
    for x in range(0,len(alist)):
        min_num = alist[x]
        for i in range(x+1,len(alist)):
            if alist[i] < min_num:
                alist[i], min_num = min_num, alist[i]
        alist[x] = min_num
    return alist
print(func([1,4,2,3,6,7,8,9,0,5]))

斐波那契

def func(n):
    a = 0
    b = 1
    alist = []
    if n <= 2:
        alist.append(a)
        alist.append(b)
        return alist
    else:
        for i in range(n):
            alist.append(a)
            a, b = b, a + b
        return alist

print(func(9))

二分法

def func(alist, item):
    low = 0
    high = len(alist)-1
    n = 0
    while low <= high:
        mid = int((low + high)/2)
        n += 1
        if alist[mid]==item:
            return mid
        if alist[mid]<item:
            low = mid + 1
        else:
            high = (mid-1)
    return None

m=[1,2,3,4,8,9,11,12,14,18,19,20,28]
print(func(m,14))

链表

class Node:
    def __init__(self, initdata):
        self.__data = initdata
        self.__next = None

    def getData(self):
        return self.__data

    def getNext(self):
        return self.__next

    def setData(self, newdata):
        self.__data = newdata

    def setNext(self, newnext):
        self.__next = newnext

class SinCycLinkedlist:
    def __init__(self):
        self.head = Node(None)
        self.head.setNext(self.head)

    def add(self, item):
        temp = Node(item)
        temp.setNext(self.head.getNext())
        self.head.setNext(temp)

    def remove(self, item):
        prev = self.head
        while prev.getNext() != self.head:
            cur = prev.getNext()
            if cur.getData() == item:
                prev.setNext(cur.getNext())
            prev = prev.getNext()

    def search(self, item):
        cur = self.head.getNext()
        while cur != self.head:
            if cur.getData() == item:
                return True
            cur = cur.getNext()

        return False

    def empty(self):
        return self.head.getNext() == self.head

    def size(self):
        count = 0
        cur = self.head.getNext()
        while cur != self.head:
            count += 1
            cur = cur.getNext()

        return count

if __name__ == '__main__':
    s = SinCycLinkedlist()
    print('s.empty() == %s, s.size() == %s' % (s.empty(), s.size()))

    s.add(19)
    s.add(86)
    print('s.empty() == %s, s.size() == %s' % (s.empty(), s.size()))

    print('86 is%s in s' % ('' if s.search(86) else ' not',))
    print('4 is%s in s' % ('' if s.search(4) else ' not',))
    print('s.empty() == %s, s.size() == %s' % (s.empty(), s.size()))

    s.remove(19)
    print('s.empty() == %s, s.size() == %s' % (s.empty(), s.size()))

青蛙跳台阶

一只青蛙一次可以跳上1级台阶，也可以跳上2级……它也可以跳上n级。求该青蛙跳上一个n级的台阶总共有多少种跳法。

fib = lambda n: n if n < 2 else 2 * fib(n - 1)

快排

#! /usr/bin/env python
# -*- coding: utf-8 -*-
def quick(list):
    if len(list) < 2:
        return list

    tmp = list[0]  # 临时变量 可以取随机值
    left = [x for x in list[1:] if x <= tmp]  # 左列表
    right = [x for x in list[1:] if x > tmp]  # 右列表
    return quick(left) + [tmp] + quick(right)

li = [4,3,7,5,8,2]
print quick(li)  # [2, 3, 4, 5, 7, 8]

#### 对[4,3,7,5,8,2]排序
'''
[3, 2] + [4] + [7, 5, 8]                 # tmp = [4]
[2] + [3] + [4] + [7, 5, 8]              # tmp = [3] 此时对[3, 2]这个列表进行排序
[2] + [3] + [4] + [5] + [7] + [8]        # tmp = [7] 此时对[7, 5, 8]这个列表进行排序
'''