From bfc780c4715383663f5a5e45fad2d2b1cf27015f Mon Sep 17 00:00:00 2001
From: Peter Chen <sanpeter992000@gmail.com>
Date: Sun, 15 Mar 2026 10:20:45 +0800
Subject: [PATCH] Implement CountItemsMatchingARule1773 with complexity
 analysis and tests

 - Move source file to proper package structure (src/main/java/com/leetcode/easy/)
 - Implement countMatches method with O(n) time and O(1) space complexity
 - Add Javadoc complexity analysis following project conventions
 - Add JUnit tests with example cases

 Algorithm: Single pass through items list, checking ruleKey against "type", "color", or "name" and matching against ruleValue.
---
 src/CountItemsMatchingARule1773.java          | 32 -------------
 .../easy/CountItemsMatchingARule1773.java     | 31 +++++++++++++
 .../easy/CountItemsMatchingARule1773Test.java | 45 +++++++++++++++++++
 3 files changed, 76 insertions(+), 32 deletions(-)
 delete mode 100644 src/CountItemsMatchingARule1773.java
 create mode 100644 src/main/java/com/leetcode/easy/CountItemsMatchingARule1773.java
 create mode 100644 src/test/java/com/leetcode/easy/CountItemsMatchingARule1773Test.java

diff --git a/src/CountItemsMatchingARule1773.java b/src/CountItemsMatchingARule1773.java
deleted file mode 100644
index 01ee50e..0000000
--- a/src/CountItemsMatchingARule1773.java
+++ /dev/null
@@ -1,32 +0,0 @@
-import java.util.ArrayList;
-import java.util.HashMap;
-import java.util.List;
-import java.util.Map;
-
-public class CountItemsMatchingARule1773 {
-    public int countMatches(List<List<String>> items, String ruleKey, String ruleValue) {
-        int res = 0;
-        Map<String, Integer> mapping = new HashMap<>();
-        mapping.put("type", 0);
-        mapping.put("color", 1);
-        mapping.put("name", 2);
-        int index = mapping.get(ruleKey);
-        for (List<String> item : items) {
-            if (item.get(index).equals(ruleValue)) {
-                res++;
-            }
-        }
-        return res;
-    }
-
-    public static void main(String[] args) {
-        List<List<String>> items = new ArrayList<>();
-        items.add(List.of("phone", "blue", "pixel"));
-        items.add(List.of("computer", "silver", "lenovo"));
-        items.add(List.of("phone", "gold", "iphone"));
-        String ruleKey = "color";
-        String ruleValue = "silver";
-        // 1
-        System.out.println(new CountItemsMatchingARule1773().countMatches(items, ruleKey, ruleValue));
-    }
-}
diff --git a/src/main/java/com/leetcode/easy/CountItemsMatchingARule1773.java b/src/main/java/com/leetcode/easy/CountItemsMatchingARule1773.java
new file mode 100644
index 0000000..53e83fc
--- /dev/null
+++ b/src/main/java/com/leetcode/easy/CountItemsMatchingARule1773.java
@@ -0,0 +1,31 @@
+// Tags: Array, String
+package com.leetcode.easy;
+
+import java.util.List;
+
+public class CountItemsMatchingARule1773 {
+    /**
+     * Let n = items.size().
+     * Time complexity: O(n)
+     * Breakdown:
+     * - Single for loop: Iterates through all items - O(n)
+     * - String comparison: O(1) per comparison (comparing with fixed ruleKey and ruleValue)
+     * Overall: O(n)
+     * <p>
+     * Space complexity: O(1)
+     * - Only uses a single integer variable 'res' - O(1)
+     */
+    public int countMatches(List<List<String>> items, String ruleKey, String ruleValue) {
+        int res = 0;
+        for (List<String> item : items) {
+            if (ruleKey.equals("type") && item.get(0).equals(ruleValue)) {
+                res++;
+            } else if (ruleKey.equals("color") && item.get(1).equals(ruleValue)) {
+                res++;
+            } else if (ruleKey.equals("name") && item.get(2).equals(ruleValue)) {
+                res++;
+            }
+        }
+        return res;
+    }
+}
diff --git a/src/test/java/com/leetcode/easy/CountItemsMatchingARule1773Test.java b/src/test/java/com/leetcode/easy/CountItemsMatchingARule1773Test.java
new file mode 100644
index 0000000..544042b
--- /dev/null
+++ b/src/test/java/com/leetcode/easy/CountItemsMatchingARule1773Test.java
@@ -0,0 +1,45 @@
+package com.leetcode.easy;
+
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+import java.util.List;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+public class CountItemsMatchingARule1773Test {
+    private CountItemsMatchingARule1773 solution;
+
+    @BeforeEach
+    void setUp() {
+        solution = new CountItemsMatchingARule1773();
+    }
+
+    @Test
+    void testCountMatches_Example1() {
+        var items = List.of(
+                List.of("phone", "blue", "pixel"),
+                List.of("computer", "silver", "lenovo"),
+                List.of("phone", "gold", "iphone")
+        );
+        String ruleKey = "color";
+        String ruleValue = "silver";
+        int expected = 1;
+        int result = solution.countMatches(items, ruleKey, ruleValue);
+        assertEquals(expected, result);
+    }
+
+    @Test
+    void testCountMatches_Example2() {
+        var items = List.of(
+                List.of("phone", "blue", "pixel"),
+                List.of("computer", "silver", "lenovo"),
+                List.of("phone", "gold", "iphone")
+        );
+        String ruleKey = "type";
+        String ruleValue = "phone";
+        int expected = 2;
+        int result = solution.countMatches(items, ruleKey, ruleValue);
+        assertEquals(expected, result);
+    }
+}