String and hash table (Python)

The art of deceiving Hu 2020-11-13 03:19:53
string hash table python


Catalog

character string :

Trie Trees :

Simple string matching algorithm :

Related exercises :

Hashtable :

LRU Cache elimination algorithm :

Related exercises :


character string :

Trie Trees :

class Trie(object):
def __init__(self):
"""
Initialize your data structure here.
"""
self.root = {}
self.end = '/'
def insert(self, word): # Insert
"""
Inserts a word into the trie.
:type word: str
:rtype: None
"""
node = self.root
for c in word:
if c not in node:
node[c] = {}
node = node[c]
node[self.end] = None
def search(self, word):# lookup
"""
Returns if the word is in the trie.
:type word: str
:rtype: bool
"""
node = self.root
for c in word:
if c not in node:
return False
node = node[c]
if self.end in node:
return True
else:
return False
def startsWith(self, prefix):# Prefix
"""
Returns if there is any word in the trie that starts with the given prefix.
:type prefix: str
:rtype: bool
"""
node = self.root
for c in prefix:
if c not in node:
return False
node = node[c]
return Tru

Simple string matching algorithm :

# Simple matching
def matchStr(strs,substrs):
i = 0
j = 0
if not substrs:
return True
if not strs:
return False
while i<len(strs) and j<len(substrs):
print 'str: ',strs[i]
print 'substr: ',substrs[j]
if strs[i]==substrs[j]:
i += 1
j += 1
else:
i = i-j+1
j = 0
if j >= len(substrs):
return True
return False
# test
a = "asdefvgty"
b = "vgt"
print matchStr(a,b)

Related exercises :

Reverse string

Write a function , Its function is to invert the input string . Input string as character array  char[]  Given in the form of .

class Solution(object):
def reverseString(self, s):
"""
:type s: List[str]
:rtype: None Do not return anything, modify s in-place instead.
"""
l = len(s)
if l<=1:
return
for i in range(l/2):
s[i],s[l-1-i] = s[l-1-i],s[i]

Flip the words in the string

Given a string , Flip each word in the string one by one .

class Solution(object):
def reverseWords(self, s):
"""
:type s: str
:rtype: str
"""
if not s:
return ""
s_list = s.split(' ')
ret_list = [i for i in s_list if i != '']
ret_list = ret_list[::-1]
return ' '.join(ret_list)

String conversion integers (atoi)

First , This function discards the useless start space characters as needed , Until the first non space character is found .

When the first non empty character we find is a positive or negative sign , Then combine the symbol with as many consecutive numbers as possible on the back face , As the sign of the integer ; If the first non empty character is a number , Then combine it directly with the following consecutive numeric characters , Form an integer .

class Solution(object):
def myAtoi(self, str):
"""
:type str: str
:rtype: int
"""
s = str.strip()
ret =''
if len(s)<1:
return 0
if s[0]=='-' or s[0]=='+':# Minus sign
if len(s)<=1 or not s[1].isdigit():
return 0
else:
ret += s[0]
for i in range(1,len(s)):
if s[i].isdigit():
ret += s[i]
else:
break
elif not s[0].isdigit():# Letter
return 0
else:# Numbers
for i in range(0,len(s)):
if s[i].isdigit():
ret += s[i]
else:
break
num = int(ret)
if num>2**31-1:
return 2**31-1
elif num<-2**31:
return -2**31
else:
return num

 

Hashtable :

LRU Cache elimination algorithm :

from collections import OrderedDict
class LRU():
def __init__(self,capacity = 10):
self.maxcount = capacity
self.queue = OrderedDict()
def get(self,key):
if key not in self.queue:
return -1
else:
value = self.queue.pop(key)
self.queue[key] = value
return value
def put(self,key,data):
if key in self.queue:
self.queue.pop(key)
self.queue[key] = data
else:
if len(self.queue.items()) == self.maxcount:
self.queue.popitem(last = False)
self.queue[key] = data
else:
self.queue[key] = data

Related exercises :

Sum of two numbers

Given an array of integers  nums  And a target value  target, Please find and as the target value in the array   Two   Integers , And return their array subscripts

class Solution(object):
def twoSum(self, nums, target):
"""
:type nums: List[int]
:type target: int
:rtype: List[int]
"""
mydict = {}
for i in range(len(nums)):
if target-nums[i] in mydict:
return [mydict[target-nums[i]],i]
else:
mydict[nums[i]] = i

Happy number

Write an algorithm to determine whether a number is “ Happy number ”.

One “ Happy number ” Defined as : For a positive integer , Replace the number with the sum of the squares of the numbers in each of its positions , Then repeat the process until the number becomes 1, It can also be an infinite loop but never change 1. If it can be 1, So this number is the happy number .

class Solution(object):
def isHappy(self, n):
"""
:type n: int
:rtype: bool
"""
history = []
while n>=10:
print 'n-:',n
sumnow = 0
m = 0
while n>=10:
m = n%10
n = n/10
sumnow += m*m
sumnow += n*n
n = sumnow
print 'n+:',n
return n == 1 or n == 7

 

版权声明
本文为[The art of deceiving Hu]所创,转载请带上原文链接,感谢

  1. 利用Python爬虫获取招聘网站职位信息
  2. Using Python crawler to obtain job information of recruitment website
  3. Several highly rated Python libraries arrow, jsonpath, psutil and tenacity are recommended
  4. Python装饰器
  5. Python实现LDAP认证
  6. Python decorator
  7. Implementing LDAP authentication with Python
  8. Vscode configures Python development environment!
  9. In Python, how dare you say you can't log module? ️
  10. 我收藏的有关Python的电子书和资料
  11. python 中 lambda的一些tips
  12. python中字典的一些tips
  13. python 用生成器生成斐波那契数列
  14. python脚本转pyc踩了个坑。。。
  15. My collection of e-books and materials about Python
  16. Some tips of lambda in Python
  17. Some tips of dictionary in Python
  18. Using Python generator to generate Fibonacci sequence
  19. The conversion of Python script to PyC stepped on a pit...
  20. Python游戏开发,pygame模块,Python实现扫雷小游戏
  21. Python game development, pyGame module, python implementation of minesweeping games
  22. Python实用工具,email模块,Python实现邮件远程控制自己电脑
  23. Python utility, email module, python realizes mail remote control of its own computer
  24. 毫无头绪的自学Python,你可能连门槛都摸不到!【最佳学习路线】
  25. Python读取二进制文件代码方法解析
  26. Python字典的实现原理
  27. Without a clue, you may not even touch the threshold【 Best learning route]
  28. Parsing method of Python reading binary file code
  29. Implementation principle of Python dictionary
  30. You must know the function of pandas to parse JSON data - JSON_ normalize()
  31. Python实用案例,私人定制,Python自动化生成爱豆专属2021日历
  32. Python practical case, private customization, python automatic generation of Adu exclusive 2021 calendar
  33. 《Python实例》震惊了,用Python这么简单实现了聊天系统的脏话,广告检测
  34. "Python instance" was shocked and realized the dirty words and advertisement detection of the chat system in Python
  35. Convolutional neural network processing sequence for Python deep learning
  36. Python data structure and algorithm (1) -- enum type enum
  37. 超全大厂算法岗百问百答(推荐系统/机器学习/深度学习/C++/Spark/python)
  38. 【Python进阶】你真的明白NumPy中的ndarray吗?
  39. All questions and answers for algorithm posts of super large factories (recommended system / machine learning / deep learning / C + + / spark / Python)
  40. [advanced Python] do you really understand ndarray in numpy?
  41. 【Python进阶】Python进阶专栏栏主自述:不忘初心,砥砺前行
  42. [advanced Python] Python advanced column main readme: never forget the original intention and forge ahead
  43. python垃圾回收和缓存管理
  44. java调用Python程序
  45. java调用Python程序
  46. Python常用函数有哪些?Python基础入门课程
  47. Python garbage collection and cache management
  48. Java calling Python program
  49. Java calling Python program
  50. What functions are commonly used in Python? Introduction to Python Basics
  51. Python basic knowledge
  52. Anaconda5.2 安装 Python 库(MySQLdb)的方法
  53. Python实现对脑电数据情绪分析
  54. Anaconda 5.2 method of installing Python Library (mysqldb)
  55. Python implements emotion analysis of EEG data
  56. Master some advanced usage of Python in 30 seconds, which makes others envy it
  57. python爬取百度图片并对图片做一系列处理
  58. Python crawls Baidu pictures and does a series of processing on them
  59. python链接mysql数据库
  60. Python link MySQL database