LLD for In Memor key-val store

data-structures/pom.xml

@@ -0,0 +1,14 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+    <parent>
+        <groupId>com.thealgorithm</groupId>
+        <artifactId>TheAlgorithm</artifactId>
+        <version>1.0-SNAPSHOT</version>
+    </parent>
+
+    <groupId>com.thealgorithm</groupId>
+    <artifactId>data-structures</artifactId>
+</project>

data-structures/src/main/java/com/thealgorithm/miscelleneous/GenerateParenthesis.java

@@ -0,0 +1,77 @@
+package com.thealgorithm.miscelleneous;
+
+import java.util.ArrayList;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Set;
+
+/**
+ * @author: Subham Santra
+ */
+public class GenerateParenthesis {
+
+  public List<String> generate(int c1, int c2, int c3) {
+    Set<String> result = new HashSet<>();
+    generate(c1, 0, 0, c2, 0, 0, c3, 0, 0, result, new StringBuilder());
+    return new ArrayList<>(result);
+  }
+
+  private void generate(
+      int c1,
+      int o1,
+      int e1,
+      int c2,
+      int o2,
+      int e2,
+      int c3,
+      int o3,
+      int e3,
+      Set<String> result,
+      StringBuilder comb) {
+
+    if (e1 > o1 || e2 > o2 || e3 > o3) {
+      return;
+    }
+
+    //        if (o1 == c1 && o1 == e1 && o2 == c2 && o2 == e2 && o3 == c3 && o3 == e3) {
+    if (o1 == c1 && o2 == c2 && o3 == c3) {
+      //    if (o1 == e1 && o2 == e2 && o3 == e3) {
+      result.add(comb.toString());
+      return;
+    }
+
+    if (o1 < c1) {
+      comb.append('(');
+      generate(c1, o1 + 1, e1, c2, o2, e2, c3, o3, e3, result, comb);
+      comb.deleteCharAt(comb.length() - 1);
+
+      comb.append(')');
+      generate(c1, o1, e1 + 1, c2, o2, e2, c3, o3, e3, result, comb);
+      comb.deleteCharAt(comb.length() - 1);
+    }
+
+    if (o2 < c2) {
+      comb.append('{');
+      generate(c1, o1, e1, c2, o2 + 1, e2, c3, o3, e3, result, comb);
+      comb.deleteCharAt(comb.length() - 1);
+
+      comb.append('}');
+      generate(c1, o1, e1, c2, o2, e2 + 1, c3, o3, e3, result, comb);
+      comb.deleteCharAt(comb.length() - 1);
+    }
+
+    if (o3 < c3) {
+      comb.append('[');
+      generate(c1, o1, e1, c2, o2, e2, c3, o3 + 1, e3, result, comb);
+      comb.deleteCharAt(comb.length() - 1);
+
+      comb.append(']');
+      generate(c1, o1 + 1, e1, c2, o2, e2, c3, o3, e3 + 1, result, comb);
+      comb.deleteCharAt(comb.length() - 1);
+    }
+  }
+
+  public static void main(String[] args) {
+    System.out.println(new GenerateParenthesis().generate(2, 2, 2));
+  }
+}

src/main/java/com/thealgorithm/dp/miscelleneous/LeetCode1155.java → data-structures/src/main/java/com/thealgorithm/miscelleneous/LeetCode1155.java

@@ -1,4 +1,4 @@
-package com.thealgorithm.dp.miscelleneous;
+package com.thealgorithm.miscelleneous;
 
 /**
  * @see <a

src/main/java/com/thealgorithm/dp/miscelleneous/LeetCode1235.java → data-structures/src/main/java/com/thealgorithm/miscelleneous/LeetCode1235.java

@@ -1,4 +1,4 @@
-package com.thealgorithm.dp.miscelleneous;
+package com.thealgorithm.miscelleneous;
 
 import java.util.Arrays;
 

src/main/java/com/thealgorithm/dp/miscelleneous/LeetCode1335.java → data-structures/src/main/java/com/thealgorithm/miscelleneous/LeetCode1335.java

@@ -1,4 +1,4 @@
-package com.thealgorithm.dp.miscelleneous;
+package com.thealgorithm.miscelleneous;
 
 import java.util.Arrays;
 

src/main/java/com/thealgorithm/dp/miscelleneous/LeetCode446.java → data-structures/src/main/java/com/thealgorithm/miscelleneous/LeetCode446.java

@@ -1,4 +1,4 @@
-package com.thealgorithm.dp.miscelleneous;
+package com.thealgorithm.miscelleneous;
 
 import java.util.ArrayList;
 import java.util.HashMap;

low-level-design/pom.xml

@@ -0,0 +1,14 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+    <parent>
+        <groupId>com.thealgorithm</groupId>
+        <artifactId>TheAlgorithm</artifactId>
+        <version>1.0-SNAPSHOT</version>
+    </parent>
+
+    <groupId>com.thealgorithm</groupId>
+    <artifactId>low-level-design</artifactId>
+</project>

low-level-design/src/main/java/com/thealgorithm/caching/CachingLocalTest.java

@@ -0,0 +1,42 @@
+package com.thealgorithm.caching;
+
+import java.nio.charset.StandardCharsets;
+import java.util.Scanner;
+import java.util.StringTokenizer;
+
+/**
+ * @author: Subham Santra
+ */
+public class CachingLocalTest {
+  public static void main(String[] args) {
+    InMemoryKeyValStore keyValStore = InMemoryKeyValStore.create();
+    try (Scanner scanner = new Scanner(System.in)) {
+
+      do {
+        String line = scanner.nextLine();
+        StringTokenizer tokenizer = new StringTokenizer(line);
+
+        String var1 = tokenizer.nextToken();
+        String var2 = tokenizer.nextToken();
+        String var3 = tokenizer.hasMoreTokens() ? tokenizer.nextToken() : "";
+        String var4 = tokenizer.hasMoreTokens() ? tokenizer.nextToken() : "";
+
+        try {
+          if (var1.equalsIgnoreCase("put")) {
+            if (var4.isBlank()) {
+              keyValStore.put(var2, var3.getBytes(StandardCharsets.UTF_8), 60_000L);
+            } else {
+              keyValStore.put(var2, var3.getBytes(StandardCharsets.UTF_8), Long.parseLong(var4));
+            }
+          } else if (var1.equalsIgnoreCase("get")) {
+            System.out.println(new String(keyValStore.get(var2)));
+          } else if (var1.equalsIgnoreCase("rem")) {
+            keyValStore.rem(var2);
+          }
+        } catch (DataNotPresentException | DataExpiredException e) {
+          System.err.println(e.getMessage());
+        }
+      } while (scanner.hasNextLine());
+    }
+  }
+}

low-level-design/src/main/java/com/thealgorithm/caching/DataExpiredException.java

@@ -0,0 +1,10 @@
+package com.thealgorithm.caching;
+
+/**
+ * @author: Subham Santra
+ */
+public class DataExpiredException extends Exception {
+  public DataExpiredException(String s) {
+    super(s);
+  }
+}

low-level-design/src/main/java/com/thealgorithm/caching/DataNotPresentException.java

@@ -0,0 +1,10 @@
+package com.thealgorithm.caching;
+
+/**
+ * @author: Subham Santra
+ */
+public class DataNotPresentException extends Exception {
+  public DataNotPresentException(String s) {
+    super(s);
+  }
+}

low-level-design/src/main/java/com/thealgorithm/caching/InMemoryKeyValStore.java

@@ -0,0 +1,60 @@
+package com.thealgorithm.caching;
+
+import java.util.Map;
+import java.util.concurrent.ConcurrentHashMap;
+import lombok.Value;
+
+/**
+ * @author: Subham Santra
+ * @apiNote
+ *     <li>$ put key val
+ *     <li>$ put key val ttl_in_seconds
+ *     <li>$ get key
+ *     <li>$ rem key
+ */
+public class InMemoryKeyValStore {
+  @Value
+  private static class Entry {
+    byte[] val;
+    long created;
+    long ttl_millis;
+  }
+
+  private final Map<String, Entry> kvStore;
+
+  private InMemoryKeyValStore() {
+    kvStore = new ConcurrentHashMap<>();
+  }
+
+  public static InMemoryKeyValStore create() {
+    return new InMemoryKeyValStore();
+  }
+
+  void put(String key, byte[] val, long ttl) {
+    kvStore.put(key, new Entry(val, System.currentTimeMillis(), ttl));
+  }
+
+  byte[] get(String key) throws DataNotPresentException, DataExpiredException {
+    if (!kvStore.containsKey(key)) {
+      throw new DataNotPresentException("'key' : " + key + " do not present");
+    }
+
+    Entry e = kvStore.get(key);
+    if (System.currentTimeMillis() - e.created > e.ttl_millis) {
+      kvStore.remove(key);
+      throw new DataExpiredException("'key' : " + key + " expired");
+    }
+
+    return e.val;
+  }
+
+  boolean rem(String key) throws DataNotPresentException, DataExpiredException {
+    if (!kvStore.containsKey(key)) {
+      throw new DataNotPresentException("'key' : " + key + " do not present");
+    }
+
+    Entry e = kvStore.get(key);
+    kvStore.remove(key);
+    return (System.currentTimeMillis() - e.created <= e.ttl_millis);
+  }
+}

pom.xml

@@ -7,6 +7,11 @@
     <groupId>com.thealgorithm</groupId>
     <artifactId>TheAlgorithm</artifactId>
     <version>1.0-SNAPSHOT</version>
+    <packaging>pom</packaging>
+    <modules>
+        <module>data-structures</module>
+        <module>low-level-design</module>
+    </modules>
 
     <properties>
         <maven.compiler.source>21</maven.compiler.source>