feat(chore): Coding Assessments for IBM [Sep-2026]

.mvn/maven.config

@@ -1,2 +1,3 @@
 -T4
--ntp
+-ntp
+-Dmaven.compiler.fork=true

Makefile

@@ -0,0 +1,7 @@
+.PHONY: tests releases
+
+tests:
+	mvn clean install test
+
+releases:
+	mvn clean install verify test jacoco:report

pom.xml

@@ -34,7 +34,7 @@
 
     <buildtime.output.log>true</buildtime.output.log>
 
-    <lombok.version>1.18.32</lombok.version>
+    <lombok.version>1.18.40</lombok.version>
     <mockito.version>5.20.0</mockito.version>
     <junit-jupiter.version>5.10.2</junit-jupiter.version>
     <junit-platform.version>1.10.2</junit-platform.version>
@@ -135,6 +135,12 @@
       <version>${junit-platform.version}</version>
       <scope>test</scope>
     </dependency>
+    <dependency>
+      <groupId>org.junit.platform</groupId>
+      <artifactId>junit-platform-suite-api</artifactId>
+      <version>${junit-platform.version}</version>
+      <scope>test</scope>
+    </dependency>
     <dependency>
       <groupId>org.instancio</groupId>
       <artifactId>instancio-junit</artifactId>
@@ -242,8 +248,16 @@
           <source>${java.version}</source>
           <target>${java.version}</target>
           <showWarnings>false</showWarnings>
+          <release>${java.version}</release>
           <showDeprecation>false</showDeprecation>
           <encoding>${project.build.sourceEncoding}</encoding>
+          <annotationProcessorPaths>
+            <path>
+              <groupId>org.projectlombok</groupId>
+              <artifactId>lombok</artifactId>
+              <version>${lombok.version}</version>
+            </path>
+          </annotationProcessorPaths>
         </configuration>
       </plugin>
       <plugin>
@@ -259,6 +273,10 @@
             <exclude>*com.shortthirdman.primekit.common.*</exclude>
             <exclude>*com.shortthirdman.primekit.core.*</exclude>
           </excludes>
+          <argLine>
+            -Dnet.bytebuddy.experimental=true
+            --add-opens java.net.http/java.net.http=ALL-UNNAMED
+          </argLine>
           <properties>
             <configurationParameters>
               junit.jupiter.extensions.autodetection.enabled = true

src/main/java/com/shortthirdman/primekit/hackerearth/TokenExpiryTracker.java

@@ -0,0 +1,91 @@
+package com.shortthirdman.primekit.hackerearth;
+
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.Objects;
+
+/**
+ * Manages the lifecycle, renewal, and state evaluation of authentication tokens.
+ * <p>
+ * This class tracks token creation and reset commands over discrete time units,
+ * enforcing global expiration limits and determining token availability at the
+ * conclusion of event processing.
+ * </p>
+ *
+ * @author ShortThirdMan
+ * @since 1.2.1
+ */
+public class TokenExpiryTracker {
+
+    private static final int CMD_TYPE_INDEX = 0;
+    private static final int CMD_TOKEN_ID_INDEX = 1;
+    private static final int CMD_TIME_INDEX = 2;
+
+    private static final int ACTION_CREATE = 0;
+    private static final int ACTION_RESET = 1;
+
+    /**
+     * Calculates the number of tokens that remain active after executing all specified commands.
+     * <p>
+     * A token is active immediately upon creation at time {@code T} and expires at {@code T + expiryLimit}.
+     * Subsequent reset commands at time {@code T} are valid only if the token already exists and has not yet
+     * expired (i.e., its current expiration time is greater than or equal to {@code T}).
+     * </p>
+     * <p>
+     * After processing all commands, a token is considered active if its expiration time is strictly
+     * greater than the timestamp of the last executed command.
+     * </p>
+     *
+     * @param expiryLimit the fixed lifespan added to the execution timestamp upon token creation or reset;
+     *                    must be greater than or equal to 1
+     * @param commands    a chronological list of 3-element integer tuples representing operations:
+     *                    <ul>
+     *                      <li>{@code [0, tokenId, T]} - Creates a new token with ID {@code tokenId} at time {@code T}.</li>
+     *                      <li>{@code [1, tokenId, T]} - Resets the expiration of an existing token with ID {@code tokenId} at time {@code T}.</li>
+     *                    </ul>
+     *                    Must be sorted in non-decreasing order of {@code T}.
+     * @return the total count of active tokens remaining after all commands have been evaluated;
+     *         returns {@code 0} if {@code commands} is empty
+     * @throws NullPointerException     if {@code commands} is {@code null} or contains {@code null} entries
+     * @throws IllegalArgumentException if {@code expiryLimit} is non-positive or if any command does not
+     *                                  contain exactly three elements
+     */
+    public int numberOfTokens(int expiryLimit, List<List<Integer>> commands) {
+        Objects.requireNonNull(commands, "commands list must not be null");
+        if (expiryLimit <= 0) {
+            throw new IllegalArgumentException("expiryLimit must be positive: " + expiryLimit);
+        }
+        if (commands.isEmpty()) {
+            return 0;
+        }
+
+        Map<Integer, Integer> tokenExpiries = new HashMap<>();
+
+        for (List<Integer> cmd : commands) {
+            Objects.requireNonNull(cmd, "command entry must not be null");
+            if (cmd.size() != 3) {
+                throw new IllegalArgumentException("Command must contain exactly 3 integers: [type, tokenId, T]");
+            }
+
+            int type = cmd.get(CMD_TYPE_INDEX);
+            int tokenId = cmd.get(CMD_TOKEN_ID_INDEX);
+            int timestamp = cmd.get(CMD_TIME_INDEX);
+
+            if (type == ACTION_CREATE) {
+                tokenExpiries.put(tokenId, timestamp + expiryLimit);
+            } else if (type == ACTION_RESET) {
+                Integer currentExpiry = tokenExpiries.get(tokenId);
+                if (currentExpiry != null && currentExpiry >= timestamp) {
+                    tokenExpiries.put(tokenId, timestamp + expiryLimit);
+                }
+            }
+        }
+
+        int finalTimestamp = commands.getLast().get(CMD_TIME_INDEX);
+
+        return (int) tokenExpiries.values().stream()
+                .filter(expiry -> expiry > finalTimestamp)
+                .count();
+    }
+}

src/main/java/com/shortthirdman/primekit/hackerearth/UpgradeEnhancementOptimizer.java

@@ -0,0 +1,85 @@
+package com.shortthirdman.primekit.hackerearth;
+
+import java.util.List;
+import java.util.Objects;
+
+/**
+ * Solves the optimal upgrade selection problem under a fixed currency constraint.
+ *
+ * <p>Each available upgrade index {@code i} incurs a given cost and yields an
+ * enhancement gain equal to {@code 2^i}[cite: 1]. Because every power of two is strictly greater
+ * than the sum of all preceding powers of two (i.e., {@code \sum_{j=0}^{i-1} 2^j = 2^i - 1 < 2^i}),
+ * the problem exhibits the greedy-choice property. This optimizer selects upgrades
+ * greedily starting from the highest available power down to zero.
+ *
+ * <p><strong>Thread Safety:</strong> This class is stateless, immutable, and thread-safe.
+ *
+ * @since 1.2.1
+ * @author ShortThirdMan
+ */
+public class UpgradeEnhancementOptimizer {
+
+    private static final int MOD = 1_000_000_007;
+
+    /**
+     * Calculates the maximum enhancement obtainable without exceeding the provided budget.
+     *
+     * <p>Enhancement values grow exponentially such that the item at index {@code i}
+     * contributes {@code 2^i} enhancement[cite: 1]. The returned sum is reduced modulo {@code 10^9 + 7}[cite: 1].
+     *
+     * <h4>Algorithm Details</h4>
+     * <ul>
+     *   <li><strong>Precomputes</strong> powers of two modulo {@code 1,000,000,007}.</li>
+     *   <li><strong>Greedy Selection:</strong> Evaluates items in descending index order
+     *       ({@code n - 1} down to {@code 0}), deducting the item cost whenever sufficient
+     *       budget remains.</li>
+     * </ul>
+     *
+     * <h4>Complexity</h4>
+     * <ul>
+     *   <li>Time Complexity: {@code O(n)}, where {@code n} is the size of {@code upgradeCosts}.</li>
+     *   <li>Space Complexity: {@code O(n)} auxiliary memory for modular exponent precomputations.</li>
+     * </ul>
+     *
+     * @param upgradeCosts non-null list of non-negative integers representing upgrade costs,
+     *                     where element at index {@code i} yields enhancement {@code 2^i}[cite: 1]
+     * @param budget       maximum spendable currency, must be non-negative
+     * @return the maximum enhancement score achievable within budget, modulo {@code 10^9 + 7}[cite: 1]
+     * @throws NullPointerException     if {@code upgradeCosts} is {@code null}
+     * @throws IllegalArgumentException if {@code budget} is negative
+     */
+    public int optimizeInAppUpgrades(List<Integer> upgradeCosts, int budget) {
+        Objects.requireNonNull(upgradeCosts, "upgradeCosts must not be null");
+        if (budget < 0) {
+            throw new IllegalArgumentException("budget cannot be negative: " + budget);
+        }
+
+        int n = upgradeCosts.size();
+        if (n == 0) {
+            return 0;
+        }
+
+        // Precompute powers of 2: 2^0, 2^1, ..., 2^(n-1) modulo 10^9 + 7
+        int[] pow2 = new int[n];
+        pow2[0] = 1;
+        for (int i = 1; i < n; i++) {
+            pow2[i] = (pow2[i - 1] * 2) % MOD;
+        }
+
+        long remainingBudget = budget;
+        int totalEnhancement = 0;
+
+        for (int i = n - 1; i >= 0; i--) {
+            int cost = upgradeCosts.get(i);
+            if (remainingBudget >= cost) {
+                remainingBudget -= cost;
+                totalEnhancement += pow2[i];
+                if (totalEnhancement >= MOD) {
+                    totalEnhancement -= MOD;
+                }
+            }
+        }
+
+        return totalEnhancement;
+    }
+}

src/main/java/com/shortthirdman/primekit/leetcode/WordLadders.java

@@ -18,7 +18,7 @@ public class WordLadders {
      * @param beginWord the word to begin with
      * @param endWord the word to end with
      * @param wordList the list of words
-     * @return
+     * @return the list of ladders
      */
     public List<List<String>> findLadders(String beginWord, String endWord, List<String> wordList) {
         List<List<String>> result = new ArrayList<>();
@@ -33,7 +33,7 @@ public List<List<String>> findLadders(String beginWord, String endWord, List<Str
         while (!queue.isEmpty()) {
             LinkedWordNode top = queue.poll();
 
-            //top if have shorter result already
+            //top if you have shorter result already
             if (!result.isEmpty() && top.getDepth() > minLen) {
                 return result;
             }
@@ -61,7 +61,7 @@ public List<List<String>> findLadders(String beginWord, String endWord, List<Str
                         Collections.reverse(aResult);
                         result.add(aResult);
 
-                        //stop if get shorter result
+                        //stop if you get shorter result
                         if (top.getDepth() <= minLen) {
                             minLen = top.getDepth();
                         } else {

src/test/java/com/shortthirdman/primekit/PrimeKitCodeSignalSuite.java

@@ -0,0 +1,13 @@
+package com.shortthirdman.primekit;
+
+import org.junit.platform.suite.api.IncludeClassNamePatterns;
+import org.junit.platform.suite.api.SelectPackages;
+import org.junit.platform.suite.api.Suite;
+import org.junit.platform.suite.api.SuiteDisplayName;
+
+@Suite
+@SuiteDisplayName("CodeSignal JUnit Platform Suite")
+@SelectPackages("com.shortthirdman.primekit.codesignal")
+@IncludeClassNamePatterns(".*Test")
+class PrimeKitCodeSignalSuite {
+}

src/test/java/com/shortthirdman/primekit/PrimeKitCoderByteSuite.java

@@ -0,0 +1,13 @@
+package com.shortthirdman.primekit;
+
+import org.junit.platform.suite.api.IncludeClassNamePatterns;
+import org.junit.platform.suite.api.SelectPackages;
+import org.junit.platform.suite.api.Suite;
+import org.junit.platform.suite.api.SuiteDisplayName;
+
+@Suite
+@SuiteDisplayName("CoderByte JUnit Platform Suite")
+@SelectPackages("com.shortthirdman.primekit.coderbyte")
+@IncludeClassNamePatterns(".*Test")
+class PrimeKitCoderByteSuite {
+}

src/test/java/com/shortthirdman/primekit/PrimeKitCodilitySuite.java

@@ -0,0 +1,13 @@
+package com.shortthirdman.primekit;
+
+import org.junit.platform.suite.api.IncludeClassNamePatterns;
+import org.junit.platform.suite.api.SelectPackages;
+import org.junit.platform.suite.api.Suite;
+import org.junit.platform.suite.api.SuiteDisplayName;
+
+@Suite
+@SuiteDisplayName("Codility JUnit Platform Suite")
+@SelectPackages("com.shortthirdman.primekit.codility")
+@IncludeClassNamePatterns(".*Test")
+class PrimeKitCodilitySuite {
+}

src/test/java/com/shortthirdman/primekit/PrimeKitHackerEarthSuite.java

@@ -0,0 +1,13 @@
+package com.shortthirdman.primekit;
+
+import org.junit.platform.suite.api.IncludeClassNamePatterns;
+import org.junit.platform.suite.api.SelectPackages;
+import org.junit.platform.suite.api.Suite;
+import org.junit.platform.suite.api.SuiteDisplayName;
+
+@Suite
+@SuiteDisplayName("HackerEarth JUnit Platform Suite")
+@SelectPackages("com.shortthirdman.primekit.hackerearth")
+@IncludeClassNamePatterns(".*Test")
+class PrimeKitHackerEarthSuite {
+}

src/test/java/com/shortthirdman/primekit/PrimeKitHackerRankSuite.java

@@ -0,0 +1,13 @@
+package com.shortthirdman.primekit;
+
+import org.junit.platform.suite.api.IncludeClassNamePatterns;
+import org.junit.platform.suite.api.SelectPackages;
+import org.junit.platform.suite.api.Suite;
+import org.junit.platform.suite.api.SuiteDisplayName;
+
+@Suite
+@SuiteDisplayName("HackerRank JUnit Platform Suite")
+@SelectPackages("com.shortthirdman.primekit.hackerrank")
+@IncludeClassNamePatterns(".*Test")
+class PrimeKitHackerRankSuite {
+}

src/test/java/com/shortthirdman/primekit/PrimeKitLeetCodeSuite.java

@@ -0,0 +1,13 @@
+package com.shortthirdman.primekit;
+
+import org.junit.platform.suite.api.IncludeClassNamePatterns;
+import org.junit.platform.suite.api.SelectPackages;
+import org.junit.platform.suite.api.Suite;
+import org.junit.platform.suite.api.SuiteDisplayName;
+
+@Suite
+@SuiteDisplayName("LeetCode JUnit Platform Suite")
+@SelectPackages("com.shortthirdman.primekit.leetcode")
+@IncludeClassNamePatterns(".*Test")
+class PrimeKitLeetCodeSuite {
+}