<OFFER05> 05_ReplaceSpaces替换空格

/*******************************************************************
Copyright(c) 2016, Harry He
All rights reserved.

Distributed under the BSD license.
(See accompanying file LICENSE.txt at
https://github.com/zhedahht/CodingInterviewChinese2/blob/master/LICENSE.txt)
*******************************************************************/

//==================================================================
// 《剑指Offer——名企面试官精讲典型编程题》代码
// 作者：何海涛
//==================================================================

// 面试题5：替换空格
// 题目：请实现一个函数，把字符串中的每个空格替换成"%20"。例如输入“We are happy.”，
// 则输出“We%20are%20happy.”。

#include <cstdio>
#include <cstring>
#if 0

/*length 为字符数组str的总容量，大于或等于字符串str的实际长度*/
void ReplaceBlank(char str[], int length)
{
    if (str == nullptr && length <= 0)
        return;

    /*originalLength 为字符串str的实际长度*/
    int originalLength = 0;
    int numberOfBlank = 0;
    int i = 0;
    while (str[i] != '\0')
    {
        ++originalLength;

        if (str[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 (str[indexOfOriginal] == ' ')
        {
            str[indexOfNew--] = '0';
            str[indexOfNew--] = '2';
            str[indexOfNew--] = '%';
        }
        else
        {
            str[indexOfNew--] = str[indexOfOriginal];
        }

        --indexOfOriginal;
    }
}

#endif


#if 1
/*length 为字符数组str的总容量，大于或等于字符串str的实际长度*/
void ReplaceBlank(char str[], int length)
{
    if ((str == nullptr) || (length < 0))
        return;

    //在原来字符串上进行替换，length保证开够了空间
    int length_of_origin = 0;
    int length_of_blank = 0;
    int i = 0;

    //如何知道字符串的长度
    while (str[i] != '\0')
    {
        if (str[i] == ' ')
        {
            length_of_blank++;
        }
        length_of_origin++;
        i++;
    }

    int length_new = length_of_origin + 2 * length_of_blank;

    int p1 = length_of_origin;
    int p2 = length_new;

    while (p2 > p1)
    {
        if (str[p1] != ' ')
        {
            str[p2] = str[p1];

            p2--;
            p1--;
        }
        else
        {
            p1--;
            str[p2--] = '0';
            str[p2--] = '2';
            str[p2--] = '%';
        }
    }


    
}
#endif

// ====================测试代码====================
void Test(char* testName, char str[], int length, char expected[])
{
    if (testName != nullptr)
        printf("%s begins: ", testName);

    ReplaceBlank(str, length);

    if (expected == nullptr && str == nullptr)
        printf("passed.\n");
    else if (expected == nullptr && str != nullptr)
        printf("failed.\n");
    else if (strcmp(str, expected) == 0)
        printf("passed.\n");
    else
        printf("failed.\n");
}

// 空格在句子中间
void Test1()
{
    const int length = 100;

    char str[length] = "hello world";
    Test("Test1", str, length, "hello%20world");
}

// 空格在句子开头
void Test2()
{
    const int length = 100;

    char str[length] = " helloworld";
    Test("Test2", str, length, "%20helloworld");
}

// 空格在句子末尾
void Test3()
{
    const int length = 100;

    char str[length] = "helloworld ";
    Test("Test3", str, length, "helloworld%20");
}

// 连续有两个空格
void Test4()
{
    const int length = 100;

    char str[length] = "hello  world";
    Test("Test4", str, length, "hello%20%20world");
}

// 传入nullptr
void Test5()
{
    Test("Test5", nullptr, 0, nullptr);
}

// 传入内容为空的字符串
void Test6()
{
    const int length = 100;

    char str[length] = "";
    Test("Test6", str, length, "");
}

//传入内容为一个空格的字符串
void Test7()
{
    const int length = 100;

    char str[length] = " ";
    Test("Test7", str, length, "%20");
}

// 传入的字符串没有空格
void Test8()
{
    const int length = 100;

    char str[length] = "helloworld";
    Test("Test8", str, length, "helloworld");
}

// 传入的字符串全是空格
void Test9()
{
    const int length = 100;

    char str[length] = "   ";
    Test("Test9", str, length, "%20%20%20");
}

int main(int argc, char* argv[])
{
    Test1();
    Test2();
    Test3();
    Test4();
    Test5();
    Test6();
    Test7();
    Test8();
    Test9();

    return 0;
}