2022-06-21 update: added "3Sum"

Author: fartem

Diff for: src/main/java/com/smlnskgmail/jaman/leetcodejava/medium/ThreeSum.java

@@ -0,0 +1,54 @@
+package com.smlnskgmail.jaman.leetcodejava.medium;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+
+// https://leetcode.com/problems/3sum/
+public class ThreeSum {
+
+    private final int[] input;
+
+    public ThreeSum(int[] input) {
+        this.input = input;
+    }
+
+    public List<List<Integer>> solution() {
+        Arrays.sort(input);
+        List<List<Integer>> result = new ArrayList<>();
+        for (int i = 0; i < input.length - 2; i++) {
+            int curr = input[i];
+            if (i > 0 && curr == input[i - 1]) {
+                continue;
+            }
+            int rem = -curr;
+            int start = i + 1;
+            int end = input.length - 1;
+            while (start < end) {
+                int s = input[start];
+                int e = input[end];
+                if (s + e == rem) {
+                    List<Integer> part = new ArrayList<>();
+                    part.add(curr);
+                    part.add(s);
+                    part.add(e);
+                    result.add(part);
+                    while (start < end && input[start] == input[start + 1]) {
+                        start++;
+                    }
+                    while (start < end && input[end] == input[end - 1]) {
+                        end--;
+                    }
+                    start++;
+                    end--;
+                } else if (s + e > rem) {
+                    end--;
+                } else {
+                    start++;
+                }
+            }
+        }
+        return result;
+    }
+
+}

Diff for: src/test/java/com/smlnskgmail/jaman/leetcodejava/medium/ThreeSumTest.java

@@ -0,0 +1,19 @@
+package com.smlnskgmail.jaman.leetcodejava.medium;
+
+import org.junit.Test;
+
+import java.util.List;
+
+import static org.junit.Assert.assertEquals;
+
+public class ThreeSumTest {
+
+    @Test
+    public void defaultTest() {
+        assertEquals(
+                List.of(List.of(-1, -1, 2), List.of(-1, 0, 1)),
+                new ThreeSum(new int[]{-1, 0, 1, 2, -1, -4}).solution()
+        );
+    }
+
+}