find the difference (examplehub#149)

realDuYuanChao · github-actions · web-flow · commit d2f9f40258fb · 2021-08-08T12:02:48.000+08:00
* find the difference

* Formatted with Google Java Formatter

Co-authored-by: github-actions &lt;${GITHUB_ACTOR}@users.noreply.github.com&gt;
diff --git a/src/main/java/com/examplehub/leetcode/easy/FindTheDifference.java b/src/main/java/com/examplehub/leetcode/easy/FindTheDifference.java
@@ -0,0 +1,72 @@
+package com.examplehub.leetcode.easy;
+
+import java.util.Arrays;
+import java.util.HashSet;
+
+/** https://leetcode.com/problems/find-the-difference/ */
+public class FindTheDifference {
+  public static char solution1(String s, String t) {
+    char[] firstChars = s.toCharArray();
+    char[] secondChars = t.toCharArray();
+    Arrays.sort(firstChars);
+    Arrays.sort(secondChars);
+    for (int i = 0; i < firstChars.length; ++i) {
+      if (firstChars[i] != secondChars[i]) {
+        return secondChars[i];
+      }
+    }
+    return secondChars[secondChars.length - 1];
+  }
+
+  public static char solution2(String s, String t) {
+    int[] countTab = new int[26];
+    for (char ch : s.toCharArray()) {
+      countTab[ch - 'a']++;
+    }
+    for (char ch : t.toCharArray()) {
+      countTab[ch - 'a']--;
+      if (countTab[ch - 'a'] < 0) {
+        return ch;
+      }
+    }
+    return ' ';
+  }
+
+  public static char solution3(String s, String t) {
+    int sum = 0;
+    for (char ch : t.toCharArray()) {
+      sum += ch;
+    }
+    for (char ch : s.toCharArray()) {
+      sum -= ch;
+    }
+    return (char) sum;
+  }
+
+  public static char solution4(String s, String t) {
+    int ret = 0;
+    for (int i = 0; i < s.length(); ++i) {
+      ret ^= s.charAt(i);
+    }
+    for (int i = 0; i < t.length(); ++i) {
+      ret ^= t.charAt(i);
+    }
+    return (char) ret;
+  }
+
+  public static char solution5(String s, String t) {
+    s = s + t;
+    HashSet<Character> set = new HashSet<>();
+    for (char ch : s.toCharArray()) {
+      if (set.contains(ch)) {
+        set.remove(ch);
+      } else {
+        set.add(ch);
+      }
+    }
+    for (char ch : set) {
+      return ch;
+    }
+    return ' ';
+  }
+}
diff --git a/src/test/java/com/examplehub/leetcode/easy/FindTheDifferenceTest.java b/src/test/java/com/examplehub/leetcode/easy/FindTheDifferenceTest.java
@@ -0,0 +1,47 @@
+package com.examplehub.leetcode.easy;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+import org.junit.jupiter.api.Test;
+
+class FindTheDifferenceTest {
+  @Test
+  void testSolution1() {
+    assertEquals('e', FindTheDifference.solution1("abcd", "abcde"));
+    assertEquals('y', FindTheDifference.solution1("", "y"));
+    assertEquals('a', FindTheDifference.solution1("a", "aa"));
+    assertEquals('a', FindTheDifference.solution1("ae", "aea"));
+  }
+
+  @Test
+  void testSolution2() {
+    assertEquals('e', FindTheDifference.solution2("abcd", "abcde"));
+    assertEquals('y', FindTheDifference.solution2("", "y"));
+    assertEquals('a', FindTheDifference.solution2("a", "aa"));
+    assertEquals('a', FindTheDifference.solution2("ae", "aea"));
+  }
+
+  @Test
+  void testSolution3() {
+    assertEquals('e', FindTheDifference.solution3("abcd", "abcde"));
+    assertEquals('y', FindTheDifference.solution3("", "y"));
+    assertEquals('a', FindTheDifference.solution3("a", "aa"));
+    assertEquals('a', FindTheDifference.solution3("ae", "aea"));
+  }
+
+  @Test
+  void testSolution4() {
+    assertEquals('e', FindTheDifference.solution4("abcd", "abcde"));
+    assertEquals('y', FindTheDifference.solution4("", "y"));
+    assertEquals('a', FindTheDifference.solution4("a", "aa"));
+    assertEquals('a', FindTheDifference.solution4("ae", "aea"));
+  }
+
+  @Test
+  void testSolution5() {
+    assertEquals('e', FindTheDifference.solution5("abcd", "abcde"));
+    assertEquals('y', FindTheDifference.solution5("", "y"));
+    assertEquals('a', FindTheDifference.solution5("a", "aa"));
+    assertEquals('a', FindTheDifference.solution5("ae", "aea"));
+  }
+}
