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Add Algorithm
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‎src/test/java/algorithm/CharacterCompressWithLength.java‎

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package algorithm;
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import org.junit.Test;
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import static org.hamcrest.CoreMatchers.is;
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import static org.junit.Assert.assertThat;
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public class CharacterCompressWithLength {
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@Test
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public void test() {
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assertThat("", is(testFunction()));
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}
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public String testFunction() {
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return "";
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}
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}

‎src/test/java/algorithm/IsAnagram.java‎

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package algorithm;
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import org.junit.Test;
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import java.util.HashMap;
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import java.util.Map;
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import static org.hamcrest.CoreMatchers.is;
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import static org.junit.Assert.assertThat;
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public class IsAnagram {
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/*
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TASK
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주어진 문자열이 애너그램인지를 판단한다.
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*/
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// 방법 1. O(nlogn) : 정렬 후에 비교하기
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// 방법 2. O(n) : 문자열 개수를 세서 비교하기
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@Test
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public void 애너그램판별하기() {
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assertThat(true, is(애너그램판별_USE_MAP("arc", "car")));
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assertThat(true, is(애너그램판별_USE_MAP("caaabbb", "abababc")));
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assertThat(false, is(애너그램판별_USE_MAP("caabbbb", "abababc")));
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assertThat(false, is(애너그램판별_USE_MAP("arc", "carr")));
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assertThat(false, is(애너그램판별_USE_MAP("arc", "caz")));
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}
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private boolean 애너그램판별_USE_MAP(String str1, String str2) {
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if (str1.length() != str2.length()) return false;
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Map<Character, Integer> strMap = new HashMap<Character, Integer>();
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for (char c : str1.toCharArray()) {
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if (strMap.containsKey(c)) {
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strMap.put(c, strMap.get(c) + 1);
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} else {
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strMap.put(c, 1);
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}
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}
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for (char c : str2.toCharArray()) {
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if (!strMap.containsKey(c)) {
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return false;
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}
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if (strMap.get(c) == 0) {
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return false;
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}
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strMap.put(c, strMap.get(c) - 1);
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}
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return true;
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}
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}

‎src/test/java/algorithm/StringParseToInt.java‎

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package algorithm;
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import org.junit.Test;
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import static org.hamcrest.CoreMatchers.is;
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import static org.junit.Assert.assertThat;
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public class StringParseToInt {
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/*
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TASK
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주어진 문자열을 int 형으로 변환한다.
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*/
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@Test
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public void toIntFromString() {
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assertThat(123, is(toIntFromString("123")));
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}
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private int toIntFromString(String str) {
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// return Integer.parseInt(str);
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char[] strArr = str.toCharArray();
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int base = 0;
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for (char c : strArr) {
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base *= 10;
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base += c - '0';
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}
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return base;
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}
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}

‎src/test/java/algorithm/UniqueCharacterInString.java‎

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package algorithm;
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import org.junit.Test;
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import java.util.HashSet;
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import java.util.Set;
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import static org.hamcrest.CoreMatchers.is;
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import static org.junit.Assert.assertThat;
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public class UniqueCharacterInString {
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/*
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TASK
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주어진 문자열에서 문자열을 구성하고 있는 각각의 문자열들이 고유한지를 판단한다.
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*/
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@Test
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public void 문자열내에서_각문자열이_고유한가() {
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assertThat(true, is(이중포문을_사용한_방법("abcd")));
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assertThat(true, is(이중포문을_사용한_방법("abcdefghij")));
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assertThat(false, is(이중포문을_사용한_방법("abccde")));
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assertThat(false, is(이중포문을_사용한_방법("abca")));
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assertThat(true, is(HashSet을_사용한_방법("abcd")));
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assertThat(true, is(HashSet을_사용한_방법("abcdefghij")));
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assertThat(false, is(HashSet을_사용한_방법("abccde")));
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assertThat(false, is(HashSet을_사용한_방법("abca")));
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}
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private boolean 이중포문을_사용한_방법(String str) {
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char[] strArr = str.toCharArray();
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for (int i = 0; i < strArr.length - 1; i++) {
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for (int j = i + 1; j < strArr.length; j++) {
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if (strArr[i] == strArr[j]) return false;
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}
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}
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return true;
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}
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private boolean HashSet을_사용한_방법(String str) {
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Set<Character> strSet = new HashSet<Character>();
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for (char c : str.toCharArray()) {
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if (strSet.contains(c)) {
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return false;
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}
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strSet.add(c);
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}
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return true;
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}
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}

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