CS-1565: Check if the target sum exists (#13371)

algorithms-modules/algorithms-miscellaneous-3/src/main/java/com/baeldung/algorithms/checktargetsum/CheckTargetSum.java

@@ -0,0 +1,58 @@
+package com.baeldung.algorithms.checktargetsum;
+
+import java.util.Arrays;
+import java.util.HashSet;
+import java.util.Set;
+
+public class CheckTargetSum {
+    public boolean isTargetSumExistNaive(int[] nums, int target) {
+        for (int i = 0; i < nums.length; i++) {
+            for (int j = i + 1; j < nums.length; j++) {
+                if (nums[i] + nums[j] == target) {
+                    return true;
+                }
+            }
+        }
+
+        return false;
+    }
+
+    public boolean isTargetSumExistSorted(int[] nums, int target) {
+        Arrays.sort(nums);
+
+        int start = 0;
+        int end = nums.length - 1;
+
+        while (start < end) {
+            int sum = nums[start] + nums[end];
+
+            if (sum == target) {
+                return true;
+            }
+
+            if (sum < target) {
+                start++;
+            } else {
+                end--;
+            }
+        }
+
+        return false;
+    }
+
+    public boolean isTargetSumExistHashSet(int[] nums, int target) {
+        Set<Integer> hashSet = new HashSet<>();
+
+        for (int num : nums) {
+            int diff = target - num;
+
+            if (hashSet.contains(diff)) {
+                return true;
+            }
+
+            hashSet.add(num);
+        }
+
+        return false;
+    }
+}

algorithms-modules/algorithms-miscellaneous-3/src/test/java/com/baeldung/algorithms/checktargetsum/CheckTargetSumUnitTest.java

@@ -0,0 +1,46 @@
+package com.baeldung.algorithms.checktargetsum;
+
+import org.junit.Test;
+
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+
+public class CheckTargetSumUnitTest {
+    private CheckTargetSum checkTargetSum = new CheckTargetSum();
+
+    private int[] nums = new int[] { 10, 5, 15, 7, 14, 1, 9 };
+
+    private int existingTarget = 6;
+
+    private int nonExistingTarget = 27;
+
+    @Test
+    public void givenArrayOfIntegers_whenTargetSumNaive_thenPairExists() {
+        assertTrue(checkTargetSum.isTargetSumExistNaive(nums, existingTarget));
+    }
+
+    @Test
+    public void givenArrayOfIntegers_whenTargetSumNaive_thenPairDoesNotExists() {
+        assertFalse(checkTargetSum.isTargetSumExistNaive(nums, nonExistingTarget));
+    }
+
+    @Test
+    public void givenArrayOfIntegers_whenTargetSumSorted_thenPairExists() {
+        assertTrue(checkTargetSum.isTargetSumExistNaive(nums, existingTarget));
+    }
+
+    @Test
+    public void givenArrayOfIntegers_whenTargetSumSorted_thenPairDoesNotExists() {
+        assertFalse(checkTargetSum.isTargetSumExistNaive(nums, nonExistingTarget));
+    }
+
+    @Test
+    public void givenArrayOfIntegers_whenTargetSumHashSet_thenPairExists() {
+        assertTrue(checkTargetSum.isTargetSumExistNaive(nums, existingTarget));
+    }
+
+    @Test
+    public void givenArrayOfIntegers_whenTargetSumHashSet_thenPairDoesNotExists() {
+        assertFalse(checkTargetSum.isTargetSumExistNaive(nums, nonExistingTarget));
+    }
+}