面试题5：字符串替换空格

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All rights reserved.
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//==================================================================
// 《剑指Offer——名企面试官精讲典型编程题》C++代码
//
// 面试题5：字符串替换空格
// 题目：实现一个函数，把字符串中的每个空格替换成“%20”（空格的ASCII为32,十六进制的0x20）
//==================================================================

#include<iostream>

using namespace std;

// 功能函数
void ReplaceBlank(char string[], int length) {
    if (string == nullptr || length < 0)
        return;

    // 遍历一次得到字符串长度和空格个数
    int orignalLength = 0;
    int numberOfBlank = 0;
    int i = 0;
    while (string[i] != '\0') {
        ++orignalLength;
        if (string[i] == ' ')
            ++numberOfBlank;
        ++i;
    }

    // 把空格替换成“%20”后字符串长度为newLength
    int newLength = orignalLength + numberOfBlank * 2;
    if (newLength > length)
        return;
    int indexOfOriginal = orignalLength;
    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;
    }
}

//================================测试代码==================================
void Test(char *testName, char string[], int length, char except[]) {
    if (testName != nullptr)
        cout << testName << ":";

    ReplaceBlank(string, length);

    if (except == nullptr && string == nullptr)
        cout << "passed." << endl;
    else if (except == nullptr && string != nullptr)
        cout << "failed." << endl;
    else if(strcmp(string, except) == 0)
        cout << "passed." << endl;
    else
        cout << "failed." << endl;
}

// 输入的字符串中包含空格
void test1() {
    const int length = 100;
    char str[length] = "hello world";
    char test[] = "test1";
    char except[] = "hello%20world";
    Test(test, str, length, except);

}

// 输入的字符串中没有空格
void test2() {
    const int length = 100;
    char str[length] = "helloworld";
    char test[] = "test2";
    char except[] = "helloworld";
    Test(test, str, length, except);
}

// 字符串是个nullptr指针
void test3() {
    const int length = 0;
    char test[] = "test3";
    Test(test, nullptr, length, nullptr);
}

// 主函数
int main() {
    test1();
    test2();
    test3();
    system("pause");
    return 0;
}