面试题4: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.”

要求:在原来的字符串上做替换，并保证输入的字符串后面有足够的空余内存，常数空间复杂度。

#include <iostream>
using namespace std;


void ReplaceBlank(char string[], int maxLength)
{
	if (string == NULL || maxLength <= 0)
		return;


	int numOfBlank = 0;
	int originalLength = strlen(string);
	for (int i = 0; string[i] != '\0'; ++i)
	{
		if (string[i] == ' ')
			++numOfBlank;
	}


	int newLength = originalLength + 2 * numOfBlank;
	if (newLength > maxLength)
	{
		cout << "容量不足!" << endl;
		return;
	}


	int indexOfOriginal = originalLength - 1;
	int indexOfNew = newLength - 1;
	while (indexOfOriginal >= 0 && indexOfNew > indexOfOriginal)
	{
		if (string[indexOfOriginal] != ' ')
			string[indexOfNew--] = string[indexOfOriginal];
		else
		{
			string[indexOfNew--] = '0';
			string[indexOfNew--] = '2';
			string[indexOfNew--] = '%';
		}


		--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");
	else
		printf("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 main()
{
	Test1();
	Test2();
	Test3();
	Test4();
	Test5();
	Test6();
	Test7();
	Test8();
	Test9();


	/*
	char string[100] = "hello world";
	ReplaceBlank(string,100);
	cout << string << endl;
	*/
	return 0;
}