《剑指offer》第四题

// 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 <iostream>
using namespace std;

bool replace_space(char* str,const int length)
{
    if (str == NULL && length <= 0)//上来先判断
        return false;

    int true_length = 0, count = 0, i = 0;
    while (str[i] != '\0')//这里要用单引号
    {
        ++true_length;//输入的length是数组最大长度，真实长度有待检测
        if (str[i] == ' ')
            ++count;
        ++i;
    }

    int new_length = true_length + 2 * count;//算法核心思想，从尾到头复制
    if (new_length > length)//要判断原数组长度够长不
        return false;//难受，写的时候落下个分号

    for (int i = count; i > 0;)//当所有空格被替代完后结束
    {
        if (str[true_length] == ' ')
        {
            new_length=new_length - 2;//如果该复制空格了，先提前移两位位，并赋值“%20”，注意是两位！！
            str[new_length] = '%';//这里也要用单引号
            str[new_length+1] = '2';
            str[new_length+2] = '0';//这里也写错过，是+2，不小心写成+1！！
            i--;//这个判断条件也写错过，刚才写进for（）中了！！
        }
        else
            str[new_length] = str[true_length];

        new_length -= 1;
        true_length -= 1;

    }
    return true;
}

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

    replace_space(str, length);

    if (expected == NULL && str == NULL)
        printf("passed.\n");
    else if (expected == NULL && str != NULL)
        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();//是无效输入
    Test6();//是空输入，这俩还不太一样
    Test7();
    Test8();
    Test9();

    system("pause");
}