刷题

1、replaceSpace

算法
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题目

请实现一个函数，把字符串中的每个空格替换为”%20”。

输入

“We are happy”

输出

“We%20are%20happy”

实现

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 public static String replaceSpace(String input) {
    if (input == null) {
        return null;
    }
    if ("".equals(input)) {
        return null;
    }
    //计算空格的个数
    char[] chars = input.toCharArray();
    int numOfSpace = 0;
    for (char curChar : chars) {
        if (curChar == ' ') {
            numOfSpace++;
        }
    }
    //创建一个新的字符数组
    char[] newChars = new char[chars.length + numOfSpace * 2];
    int indexOfNewChar = -1;
    for (char curChar : chars) {
        if (curChar != ' ') {
            newChars[++indexOfNewChar] = curChar;
        } else {
            newChars[++indexOfNewChar] = '%';
            newChars[++indexOfNewChar] = '2';
            newChars[++indexOfNewChar] = '0';
        }
    }
    return String.valueOf(newChars);
}

单元测试

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package com.easyliu.test.replace_space;

import org.junit.Assert;
import org.junit.Test;

public class ReplaceSpaceTest {

    @Test
    public void testNullInput() {
        Assert.assertNull(ReplaceSpace.replaceSpace(null));
    }

    @Test
    public void testEmptyInput() {
        Assert.assertNull(ReplaceSpace.replaceSpace(""));
    }

    @Test
    public void testNormalSpace() {
        String expect = "we%20are%20happy";
        String result = ReplaceSpace.replaceSpace("we are happy");
        Assert.assertEquals(expect, result);
    }

    @Test
    public void testMultiSpace() {
        String expect = "we%20%20are%20%20happy";
        String result = ReplaceSpace.replaceSpace("we  are  happy");
        Assert.assertEquals(expect, result);
    }

    @Test
    public void testSingleSpace() {
        String expect = "%20";
        String result = ReplaceSpace.replaceSpace(" ");
        Assert.assertEquals(expect, result);
    }

    @Test
    public void testNoSpace() {
        String expect = "we";
        String result = ReplaceSpace.replaceSpace("we");
        Assert.assertEquals(expect, result);
    }
}