Updates

Author: manojbaishya

pom.xml

@@ -16,18 +16,39 @@
     </properties>
 
     <dependencies>
+        <dependency>
+            <groupId>org.apache.commons</groupId>
+            <artifactId>commons-lang3</artifactId>
+            <version>3.17.0</version>
+        </dependency>
+        <dependency>
+            <groupId>com.google.guava</groupId>
+            <artifactId>guava</artifactId>
+            <version>33.4.8-jre</version>
+        </dependency>
+        <dependency>
+            <groupId>org.apache.commons</groupId>
+            <artifactId>commons-math3</artifactId>
+            <version>3.6.1</version>
+        </dependency>
         <dependency>
             <groupId>org.apache.commons</groupId>
             <artifactId>commons-numbers-complex</artifactId>
             <version>1.2</version>
         </dependency>
 
+        <!-- Unit Tests-->
         <dependency>
             <groupId>org.junit.jupiter</groupId>
             <artifactId>junit-jupiter</artifactId>
             <version>5.12.2</version>
             <scope>test</scope>
         </dependency>
+        <dependency>
+            <groupId>org.assertj</groupId>
+            <artifactId>assertj-core</artifactId>
+            <version>3.27.3</version>
+        </dependency>
 
         <!-- Java Microbenchmark Harness-->
         <dependency>

src/main/java/org/dojo/algorithms/HashTables.java

@@ -1,6 +1,10 @@
 package org.dojo.algorithms;
 
+import org.apache.commons.lang3.tuple.Pair;
+
+import java.util.ArrayList;
 import java.util.HashMap;
+import java.util.List;
 import java.util.Map;
 import java.util.TreeMap;
 
@@ -31,4 +35,14 @@ public int[] twoSumAlt(int[] nums, int target) {
         }
         return new int[] {};
     }
+
+    public List<Pair<Integer, Integer>> twoSumAlt2(int[] nums, int target) {
+        List<Pair<Integer, Integer>> pairs = new ArrayList<>();
+        Map<Integer, Integer> lookbehind = new HashMap<>();
+        for (int i = 0; i < nums.length; i++) {
+            if (lookbehind.containsKey(target - nums[i])) pairs.add(Pair.of(lookbehind.get(target - nums[i]), i));
+            lookbehind.put(nums[i], i);
+        }
+        return pairs;
+    }
 }

src/test/java/org/dojo/algorithms/HashTablesTests.java

@@ -1,13 +1,16 @@
 package org.dojo.algorithms;
 
+import org.apache.commons.lang3.tuple.Pair;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.params.ParameterizedTest;
 import org.junit.jupiter.params.provider.Arguments;
 import org.junit.jupiter.params.provider.MethodSource;
 
 import java.util.Arrays;
+import java.util.List;
 import java.util.stream.Stream;
 
+import static org.assertj.core.api.Assertions.assertThat;
 import static org.junit.jupiter.api.Assertions.assertArrayEquals;
 
 class HashTablesTests {
@@ -32,7 +35,7 @@ void countFrequencies(int[] input, int[] expected) {
         assertArrayEquals(expected, actual);
     }
 
-    private static Stream<Arguments> testData() {
+    private static Stream<Arguments> testTwoSumData() {
         return Stream.of(
                 Arguments.of(new int[] {2, 7, 11, 15}, 9, new int[] {0, 1}),
                 Arguments.of(new int[] {3, 2, 4}, 6, new int[] {1, 2}),
@@ -46,11 +49,36 @@ private static Stream<Arguments> testData() {
     }
 
     @ParameterizedTest
-    @MethodSource("testData")
+    @MethodSource("testTwoSumData")
     public void testTwoSum(int[] inputArray, int inputTarget, int[] expected) {
         int[] actual = sut.twoSum(inputArray, inputTarget);
         System.out.printf("%s%n", Arrays.toString(expected));
         System.out.printf("%s%n", Arrays.toString(actual));
         assertArrayEquals(expected, actual);
     }
+
+    private static Stream<Arguments> testTwoSumAlt2Data() {
+        return Stream.of(
+                Arguments.of(new int[] {2, 7, 11, 15}, 9, List.of(Pair.of(0, 1))),
+                Arguments.of(new int[] {2, 7, 4, 5, 11, 15}, 9, List.of(Pair.of(0, 1), Pair.of(2, 3))),
+                Arguments.of(new int[] {3, 2, 4}, 6, List.of(Pair.of(1, 2))),
+                Arguments.of(new int[] {3, 3}, 6, List.of(Pair.of(0, 1))),
+                Arguments.of(new int[] {3, 2, 3}, 6, List.of(Pair.of(0, 2))),
+                Arguments.of(new int[] {0, 4, 3, 0}, 0, List.of(Pair.of(0, 3))),
+                Arguments.of(new int[] {-3, 4, 3, 90}, 0, List.of(Pair.of(0, 2))),
+                Arguments.of(new int[] {-1, -2, -3, -4, -5}, -8, List.of(Pair.of(2, 4))),
+                Arguments.of(new int[] {-10, -1, -18, -19}, -19, List.of(Pair.of(1, 2))),
+                Arguments.of(new int[] {1, 2, 3, 4, 5, 6}, 7, List.of(Pair.of(0, 5), Pair.of(1, 4), Pair.of(2, 3))),
+                Arguments.of(new int[] {1, 2, 3}, 100, List.of())
+        );
+    }
+
+    @ParameterizedTest
+    @MethodSource("testTwoSumAlt2Data")
+    public void testTwoSumAlt2(int[] inputArray, int inputTarget, List<Pair<Integer, Integer>> expected) {
+        List<Pair<Integer, Integer>> actual = sut.twoSumAlt2(inputArray, inputTarget);
+        assertThat(expected)
+                .withFailMessage(() -> String.format("Expected pairs: %s, but got: %s", expected, actual))
+                .containsAll(actual);
+    }
 }