面试题4:替换空格
代码如下:
1 # -*- coding: utf-8 -*- 2 """ 3 @File:Replace_spaces_1.py 4 @E-mail:364942727@qq.com 5 @Time:2019-12-20 10:54 6 @Author:Nobita 7 @Version:1.0 8 @Desciption:面试题4:替换空格 9 """ 10 11 import time 12 ''' 13 题目: 14 请实现一个函数,把字符串中的每个空格替换成“%20”。 15 例如输入“We are happy.”,则输出“We%20are%20happy.”。 16 ''' 17 18 class Solution: 19 # write code here. 20 def replaceSpaces_1(self, s): 21 '''方法一: 22 利用python自带的append()方法解题 23 ''' 24 if not isinstance(s, str) or len(s) <= 0 or s == None: 25 return '' 26 result = [] 27 for i in s: 28 if i == ' ': 29 result.append('%20') 30 else: 31 result.append(i) 32 return ''.join(result) 33 34 # write code here. 35 def replaceSpaces_2(self, s): 36 '''方法二: 37 先计算最终需要给出的长度,然后建立两个指针p1,p2;p1指向原始字符串的末尾,p2指向替换后的字符串的末尾。 38 同时移动p1,p2, 将p1指的内容逐个复制到p2, 当p1遇到空格时:在p2处插入%20,p1向前移动一个位置,p2向前移动3个位置,当p1和p2位置重合时,全部替换完成。 39 ''' 40 if not isinstance(s, str) or len(s) <= 0 or s == None: 41 return '' 42 numberOfBlack = 0 43 for i in s: 44 if i == ' ': 45 numberOfBlack += 1 46 47 originalLenth = len(s) 48 newStrLenth = 2 * numberOfBlack + originalLenth 49 indexOfOriginal = originalLenth - 1 50 indexOfNew = newStrLenth - 1 51 newStr = newStrLenth * [None] 52 while indexOfNew >= 0 and indexOfOriginal <= indexOfNew: 53 if s[indexOfOriginal] == ' ': 54 newStr[indexOfNew - 2: indexOfNew + 1] = ['%', '2', '0'] 55 indexOfNew -= 3 56 indexOfOriginal -= 1 57 else: 58 newStr[indexOfNew] = s[indexOfOriginal] 59 indexOfNew -= 1 60 indexOfOriginal -= 1 61 return ''.join(newStr) 62 63 if __name__ == '__main__': 64 s = 'We are happy.' 65 b = '' 66 for i in range(8000000): 67 b += s 68 69 #方法一运行时间: 70 startTime_1 = time.perf_counter() 71 Solution().replaceSpaces_1(b) 72 endTime_1 = time.perf_counter() 73 print('Time Used:', endTime_1 - startTime_1) 74 75 #方法二运行时间: 76 startTime_2 = time.perf_counter() 77 Solution().replaceSpaces_2(b) 78 endTime_2 = time.perf_counter() 79 print('Time Used:', endTime_2 - startTime_2)
两种方法运行时间比较结果如下:
自测代码:
1 # -*- coding: utf-8 -*- 2 """ 3 @File:test_ReplaceSpaces.py 4 @E-mail:364942727@qq.com 5 @Time:2019-12-20 13:16 6 @Author:Nobita 7 @Version:1.0 8 @Desciption:对ReplaceSpaces函数进行单元测试 9 """ 10 11 import unittest 12 from .Replace_spaces import Solution 13 14 15 class TestReplaceSpaces(unittest.TestCase): 16 # write code here. 17 def test_01_LeftSpacesStr(self): 18 '''空格在字符串左边''' 19 s = ' helloworld' 20 result_1 = Solution().replaceSpaces_1(s) 21 result_2 = Solution().replaceSpaces_2(s) 22 print('空格在字符串左边,方法一运算结果:{},方法二运算结果:{}'.format(result_1, result_2)) 23 24 def test_02_RightSpacesStr(self): 25 '''空格在字符串右边''' 26 s = 'helloworld ' 27 result_1 = Solution().replaceSpaces_1(s) 28 result_2 = Solution().replaceSpaces_2(s) 29 print('空格在字符串右边,方法一运算结果:{},方法二运算结果:{}'.format(result_1, result_2)) 30 31 def test_03_RightLeftSpacesStr(self): 32 '''空格在字符串两边''' 33 s = ' helloworld ' 34 result_1 = Solution().replaceSpaces_1(s) 35 result_2 = Solution().replaceSpaces_2(s) 36 print('空格在字符串两边,方法一运算结果:{},方法二运算结果:{}'.format(result_1, result_2)) 37 38 def test_04_MidSpacesStr(self): 39 '''空格在字符串中间''' 40 s = 'hello world' 41 result_1 = Solution().replaceSpaces_1(s) 42 result_2 = Solution().replaceSpaces_2(s) 43 print('空格在字符串中间,方法一运算结果:{},方法二运算结果:{}'.format(result_1, result_2)) 44 45 def test_05_NoneSpacesStr(self): 46 '''字符串中没有空格''' 47 s = 'helloworld' 48 result_1 = Solution().replaceSpaces_1(s) 49 result_2 = Solution().replaceSpaces_2(s) 50 print('字符串中没有空格,方法一运算结果:{},方法二运算结果:{}'.format(result_1, result_2)) 51 52 def test_06_StrIsNull(self): 53 '''空字符串''' 54 s = '' 55 result_1 = Solution().replaceSpaces_1(s) 56 result_2 = Solution().replaceSpaces_2(s) 57 print('空字符串,方法一运算结果:{},方法二运算结果:{}'.format(result_1, result_2)) 58 59 def test_07_TypeNotStr(self): 60 '''输入类型不是字符串''' 61 s = 123456789 62 result_1 = Solution().replaceSpaces_1(s) 63 result_2 = Solution().replaceSpaces_2(s) 64 print('输入类型不是字符串,方法一运算结果:{},方法二运算结果:{}'.format(result_1, result_2)) 65 66 def test_08_OnlyOneSpaceStr(self): 67 '''只输入一个空格''' 68 s = ' ' 69 result_1 = Solution().replaceSpaces_1(s) 70 result_2 = Solution().replaceSpaces_2(s) 71 print('只输入一个空格,方法一运算结果:{},方法二运算结果:{}'.format(result_1, result_2)) 72 73 74 if __name__ == '__main__': 75 unittest.main()