Python文档整理

 

ternary operator 三目运算符

a=int(input("a="))
b=int(input("b="))
max=a if a>b else b
print(max)

https://www.runoob.com/python/python-func-enumerate.html

__init__

https://www.zhihu.com/question/46973549/answer/767530541

Python中 __init__的通俗解释是什么？ - 追远·J的回答 - 知乎 https://www.zhihu.com/question/46973549/answer/767530541

while

https://blog.csdn.net/qdPython/article/details/110133545

算法

两数之和

import json
from typing import List

class Solution:
    def twoSum(self, nums: List[int], target: int) -> List[int]:  #要求返回list格式
        tmp = {}
        for k, v in enumerate(nums):  # k从0开始,v从num[0]开始
            print(k,v)
            tmp[v] = k #将list的下标和值存入字典，因为字典下标可以方便目标值和移动取值v做差
            if target - v in tmp:
                return [tmp[target - v], k] #tmp[target - v]为一个数的下标，k为另一个数的下标
            # tmp[v] = k  #关键点，利用下标来确定tmp字典里的值是来自list的

def stringToIntegerList(input):
    return json.loads(input)

def integerListToString(nums, len_of_list=None):
    if not len_of_list:
        len_of_list = len(nums)
    return json.dumps(nums[:len_of_list])

def main():
    import sys
    import io
    def readlines():
        for line in io.TextIOWrapper(sys.stdin.buffer, encoding='utf-8'):
            yield line.strip('\n') #换行终止该行输入（改行字符串属于一个单独的lines）

    lines = readlines()
    while True:
        try:
            line = next(lines) #继续下一行输入
            nums = stringToIntegerList(line);
            line = next(lines)
            target = int(line);

            ret = Solution().twoSum(nums, target)

            out = integerListToString(ret);
            print(out)
        except StopIteration:
            break

if __name__ == '__main__':
    main()

两数之和

定义一个单链表

import json
from Cython.Compiler.ExprNodes import ListNode

# Definition for singly-linked list.
class ListNode:
    def __init__(self, val=0, next=None):
        self.val = val #可变，数值
        self.next = next  #节点，指向列表的下一个数字

class Solution:
    def addTwoNumbers(self, l1: ListNode, l2: ListNode) -> ListNode:
        header = ListNode() #实例化一个"加和（链表）"对象
        p = header #现在"加和（链表）"是p
        carry = 0 #商初始化为0
        print(carry,l1,l2)
        while carry or l1 or l2: #or其中有一个为真可符合往下(不符合时结束)
            print(type(l1), type(l2))
            var = carry    ###此处是关键点：商传给余值
            print(carry, var,l1.val)  #l1.val表示l1[]，即2,4,3
            if l1:
                var = l1.val + var #这里+var余值，是满十加一
                print("var1=",var)
                l1 = l1.next #去找到下一个l1.val
            if l2:
                var = l2.val + var #这里+var是，两个链表对应位数相加
                print("+",l2.val,"=var2=", var)
                l2 = l2.next
            print(carry,var)
            carry, var = divmod(var, 10) #var/10= 商，余值 （每轮得到新的）
            print(carry,var)
            p.next = ListNode(var) #把余值存入新的链表中
            p = p.next #"加和（链表）"指向下一个，构成循环
        return header.next #逐个输出 "加和（链表）"的内容（注意有点像list，但不是list)

def stringToIntegerList(input):
    return json.loads(input)

def stringToListNode(input):
    # Generate list from the input
    numbers = stringToIntegerList(input)

    # Now convert that list into linked list
    dummyRoot = ListNode(0)
    ptr = dummyRoot
    for number in numbers:
        ptr.next = ListNode(number)
        ptr = ptr.next

    ptr = dummyRoot.next
    return ptr

def listNodeToString(node):
    if not node:
        return "[]"

    result = ""
    while node:
        result += str(node.val) + ", "
        node = node.next
    return "[" + result[:-2] + "]"

def main():
    import sys
    import io
    def readlines():
        for line in io.TextIOWrapper(sys.stdin.buffer, encoding='utf-8'):
            yield line.strip('\n')

    lines = readlines()
    while True:
        try:
            line = next(lines)
            l1 = stringToListNode(line);
            line = next(lines)
            l2 = stringToListNode(line);

            ret = Solution().addTwoNumbers(l1, l2)

            out = listNodeToString(ret);
            print(out)
        except StopIteration:
            break

if __name__ == '__main__':
    main()

运行

[2,4,3]
[8,1,1]
0 <__main__.ListNode object at 0x159dece50> <__main__.ListNode object at 0x159dfd040>
<class '__main__.ListNode'> <class '__main__.ListNode'>
0 0 2
var1= 2
+ 8 =var2= 10
0 10
1 0
<class '__main__.ListNode'> <class '__main__.ListNode'>
1 1 4
var1= 5
+ 1 =var2= 6
1 6
0 6
<class '__main__.ListNode'> <class '__main__.ListNode'>
0 0 3
var1= 3
+ 1 =var2= 4
0 4
0 4
[0, 6, 4]