【剑指】5.替换空格

题目描述

• 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.”。
  

算法分析

• 在同一个字符串中操作，判断空格个数，修改字符串空间，逆向添加字符，遇到空格替换为%20

提交代码：

class Solution {
public:
	void replaceSpace(char *str, int length) {
		if (!str)
			return;
		int blankNumber = 0;
		int originLength = 0;
		while (str[originLength] != '\0')
		{
			if (str[originLength] == ' ')
				++blankNumber;
			++originLength;
		}

		int newLength = originLength + 2 * blankNumber;
		if (newLength > length)
			return;

		int i = originLength;
		int j = newLength;
		while (i >= 0 && j >= 0)
		{
			if (str[i] != ' ')
				str[j--] = str[i];
			else
			{
				str[j--] = '0';
				str[j--] = '2';
				str[j--] = '%';
			}
			--i;
		}
	}
};

测试代码：

#include<iostream>
#include<vector>

using namespace std;
/*
// 面试题5:
请实现一个函数，将一个字符串中的空格替换成“%20”。
例如，当字符串为We Are Happy.则经过替换之后的字符串为We%20Are%20Happy。
*/
// ====================测试代码====================
void Test(char* testName, char str[], int length, char expected[])
{
	Solution s;
	if (testName != nullptr)
		printf("%s begins: ", testName);

	s.replaceSpace(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;
}