From b4bf8f1dfab5819a6342bdad30266f2ad4e196aa Mon Sep 17 00:00:00 2001
From: Peter Chen <sanpeter992000@gmail.com>
Date: Thu, 18 Sep 2025 08:48:51 +0800
Subject: [PATCH] Add solution for the "Check If Two String Arrays are
 Equivalent" problem with unit tests.

---
 ...eckIfTwoStringArraysAreEquivalent1662.java | 20 --------
 ...eckIfTwoStringArraysAreEquivalent1662.java | 13 ++++++
 ...fTwoStringArraysAreEquivalent1662Test.java | 46 +++++++++++++++++++
 3 files changed, 59 insertions(+), 20 deletions(-)
 delete mode 100644 src/CheckIfTwoStringArraysAreEquivalent1662.java
 create mode 100644 src/main/java/com/leetcode/easy/CheckIfTwoStringArraysAreEquivalent1662.java
 create mode 100644 src/test/java/com/leetcode/easy/CheckIfTwoStringArraysAreEquivalent1662Test.java

diff --git a/src/CheckIfTwoStringArraysAreEquivalent1662.java b/src/CheckIfTwoStringArraysAreEquivalent1662.java
deleted file mode 100644
index d623a6b..0000000
--- a/src/CheckIfTwoStringArraysAreEquivalent1662.java
+++ /dev/null
@@ -1,20 +0,0 @@
-public class CheckIfTwoStringArraysAreEquivalent1662 {
-    public boolean arrayStringsAreEqual(String[] word1, String[] word2) {
-        String string1 = "";
-        for (String word : word1) {
-            string1 = string1.concat(word);
-        }
-        String string2 = "";
-        for (String word : word2) {
-            string2 = string2.concat(word);
-        }
-        return string1.equals(string2);
-    }
-
-    public static void main(String[] args) {
-        String[] word1 = new String[]{"ab", "c"};
-        String[] word2 = new String[]{"a", "bc"};
-        // true
-        System.out.println(new CheckIfTwoStringArraysAreEquivalent1662().arrayStringsAreEqual(word1, word2));
-    }
-}
diff --git a/src/main/java/com/leetcode/easy/CheckIfTwoStringArraysAreEquivalent1662.java b/src/main/java/com/leetcode/easy/CheckIfTwoStringArraysAreEquivalent1662.java
new file mode 100644
index 0000000..891b2c4
--- /dev/null
+++ b/src/main/java/com/leetcode/easy/CheckIfTwoStringArraysAreEquivalent1662.java
@@ -0,0 +1,13 @@
+// Tags: Array, String
+package com.leetcode.easy;
+
+public class CheckIfTwoStringArraysAreEquivalent1662 {
+    /*
+        Let N be the maximum of the number of all characters in word1 and the number of all characters in word2.
+        Time complexity: O(N), since we need to iterate over all characters in word1 and word2 to build the new strings.
+        Space complexity: O(N), since we need extra O(N) space to store the new built strings.
+     */
+    public boolean arrayStringsAreEqual(String[] word1, String[] word2) {
+        return String.join("", word1).equals(String.join("", word2));
+    }
+}
diff --git a/src/test/java/com/leetcode/easy/CheckIfTwoStringArraysAreEquivalent1662Test.java b/src/test/java/com/leetcode/easy/CheckIfTwoStringArraysAreEquivalent1662Test.java
new file mode 100644
index 0000000..6bd11ea
--- /dev/null
+++ b/src/test/java/com/leetcode/easy/CheckIfTwoStringArraysAreEquivalent1662Test.java
@@ -0,0 +1,46 @@
+package com.leetcode.easy;
+
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+public class CheckIfTwoStringArraysAreEquivalent1662Test {
+    private CheckIfTwoStringArraysAreEquivalent1662 solution;
+
+    @BeforeEach
+    void setUp() {
+        solution = new CheckIfTwoStringArraysAreEquivalent1662();
+    }
+
+    @Test
+    void testArrayStringsAreEqual_Example1() {
+        String[] word1 = {"ab", "c"};
+        String[] word2 = {"a", "bc"};
+
+        boolean result = solution.arrayStringsAreEqual(word1, word2);
+
+        assertTrue(result);
+    }
+
+    @Test
+    void testArrayStringsAreEqual_Example2() {
+        String[] word1 = {"a", "cb"};
+        String[] word2 = {"ab", "c"};
+
+        boolean result = solution.arrayStringsAreEqual(word1, word2);
+
+        assertFalse(result);
+    }
+
+    @Test
+    void testArrayStringsAreEqual_Example3() {
+        String[] word1 = {"abc", "d", "defg"};
+        String[] word2 = {"abcddefg"};
+
+        boolean result = solution.arrayStringsAreEqual(word1, word2);
+
+        assertTrue(result);
+    }
+}