#include <iostream>// Replace blank " " with "%20"
// Note - the 'length' parameter is the maximum length of the array
void ReplaceBlanks(char str[], int length)
{if (str == NULL || length <= 0)  // 易漏点return;// Count the number of blankschar *pChar = str;int strLen = 0;int blanksCount = 0;while (*pChar++ != '\0') {   // 易错点，容易漏掉对指针的递增操作，而导致运行时的死循环。++strLen;if (*pChar == ' ')blanksCount++;}// Compute the replaced string lengthint replacedStrLen = strLen + 2 * blanksCount;if (replacedStrLen > length) {std::cout << "The char array is lack of space." << std::endl;return;}// Char pointer initializationchar *pChar2 = str + replacedStrLen - 1;pChar = str + strLen - 1;while (pChar != pChar2) {// Replace blanks with "%20"if (*pChar == ' ') {pChar2 -= 2;*pChar2 = '%';*(pChar2 + 1) = '2';*(pChar2 + 2) = '0';} else {*pChar2 = *pChar;}--pChar;--pChar2;}
}void unitest()
{char s[100] = "We are happy.";std::cout << "Before replacing blanks, the string is " << s << std::endl;ReplaceBlanks(s, 100);std::cout << "After replacing blanks, the string is " << s << std::endl;
}int main()
{unitest();return 0;
}

#!/usr/bin/python
# -*- coding: utf8 -*-# Replace blank " " with "%20"
# Note, the 'string' parameter is Python list type;
#   and the 'length' parameter is the maximum length of the array.
def replace_blanks(string, length):if string == None or length <= 0:  # 易漏点return# Count the number of blanksblanks_count = string.count(' ')string_length = len(string)# Compute the replaced string lengthreplaced_length = string_length + 2 * blanks_countif replaced_length > length:return# Extend the char list length 'string_length' with '' charactersstring += ["" for i in range(replaced_length - string_length)]# Replace each blank with "%20"original_index = string_length - 1new_index = replaced_length - 1while new_index != original_index:if string[original_index] == ' ':new_index -= 2string[new_index:new_index+3] = '%20'else:string[new_index] = string[original_index]# Update indexesnew_index -= 1original_index -= 1def unitest():test_string = "We are happy."string_lst = list(test_string)  # 易错点，不能用'str'对象替代，因为 'str' object does not support item assignment 。print "Before replacing blanks, the string is %s" % ''.join(string_lst)replace_blanks(string_lst, 100)print "After replacing blanks, the string is %s" % ''.join(string_lst)if __name__ == '__main__':unitest()

#pragma once// The following macros define the minimum required platform.  The minimum required platform
// is the earliest version of Windows, Internet Explorer etc. that has the necessary features to run
// your application.  The macros work by enabling all features available on platform versions up to and
// including the version specified.// Modify the following defines if you have to target a platform prior to the ones specified below.
// Refer to MSDN for the latest info on corresponding values for different platforms.
#ifndef _WIN32_WINNT            // Specifies that the minimum required platform is Windows Vista.
#define _WIN32_WINNT 0x0600     // Change this to the appropriate value to target other versions of Windows.
#endif

// stdafx.h : include file for standard system include files,
// or project specific include files that are used frequently, but
// are changed infrequently
//

#pragma once#include "targetver.h"#include <stdio.h>
#include <tchar.h>// TODO: reference additional headers your program requires here

// stdafx.cpp : source file that includes just the standard includes
// ReplaceBlank.pch will be the pre-compiled header
// stdafx.obj will contain the pre-compiled type information

#include "stdafx.h"// TODO: reference any additional headers you need in STDAFX.H
// and not in this file

// ReplaceBlank.cpp : Defines the entry point for the console application.
//// 《剑指Offer——名企面试官精讲典型编程题》代码
// 著作权所有者：何海涛

#include "stdafx.h"
#include <string>/*length 为字符数组string的总容量*/
void ReplaceBlank(char string[], int length)
{if(string == NULL && length <= 0)return;/*originalLength 为字符串string的实际长度*/int originalLength = 0;int numberOfBlank = 0;int i = 0;while(string[i] != '\0'){++ originalLength;if(string[i] == ' ')++ numberOfBlank;++ i;}/*newLength 为把空格替换成'%20'之后的长度*/int newLength = originalLength + numberOfBlank * 2;if(newLength > length)return;int indexOfOriginal = originalLength;int indexOfNew = newLength;while(indexOfOriginal >= 0 && indexOfNew > indexOfOriginal){if(string[indexOfOriginal] == ' '){string[indexOfNew --] = '0';string[indexOfNew --] = '2';string[indexOfNew --] = '%';}else{string[indexOfNew --] = string[indexOfOriginal];}-- indexOfOriginal;}
}void Test(char* testName, char string[], int length, char expected[])
{if(testName != NULL)printf("%s begins: ", testName);ReplaceBlank(string, length);if(expected == NULL && string == NULL)printf("passed.\n");else if(expected == NULL && string != NULL)printf("failed.\n");else if(strcmp(string, expected) == 0)printf("passed.\n");elseprintf("failed.\n");
}// 空格在句子中间
void Test1()
{const int length = 100;char string[length] = "hello world";Test("Test1", string, length, "hello%20world");
}// 空格在句子开头
void Test2()
{const int length = 100;char string[length] = " helloworld";Test("Test2", string, length, "%20helloworld");
}// 空格在句子末尾
void Test3()
{const int length = 100;char string[length] = "helloworld ";Test("Test3", string, length, "helloworld%20");
}// 连续有两个空格
void Test4()
{const int length = 100;char string[length] = "hello  world";Test("Test4", string, length, "hello%20%20world");
}// 传入NULL
void Test5()
{Test("Test5", NULL, 0, NULL);
}// 传入内容为空的字符串
void Test6()
{const int length = 100;char string[length] = "";Test("Test6", string, length, "");
}//传入内容为一个空格的字符串
void Test7()
{const int length = 100;char string[length] = " ";Test("Test7", string, length, "%20");
}// 传入的字符串没有空格
void Test8()
{const int length = 100;char string[length] = "helloworld";Test("Test8", string, length, "helloworld");
}// 传入的字符串全是空格
void Test9()
{const int length = 100;char string[length] = "   ";Test("Test9", string, length, "%20%20%20");
}int _tmain(int argc, _TCHAR* argv[])
{Test1();Test2();Test3();Test4();Test5();Test6();Test7();Test8();Test9();return 0;
}