3Sum

Author: iam-edwin

3sum/iam-edwin.java

@@ -0,0 +1,40 @@
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Map;
+import java.util.Set;
+
+class Solution {
+    public List<List<Integer>> threeSum(int[] nums) {
+        List<List<Integer>> result = new ArrayList<>();
+
+        Map<Integer, Integer> counter = new HashMap<>();
+        for (int num : nums) {
+            int count = counter.getOrDefault(num, 0);
+            counter.put(num, count + 1);
+        }
+
+        Set<Integer> keySet = new HashSet<>(counter.keySet());
+        for (int num1 : keySet) {
+            int num1Count = counter.get(num1);
+            if (num1Count > 1) {
+                counter.put(num1, num1Count - 1);
+            } else {
+                counter.remove(num1);
+            }
+
+            for (int num2 : counter.keySet()) {
+                int num3 = -num1 - num2;
+                int count = counter.getOrDefault(num3, 0);
+                if (((num2 == num3 && count >= 2) || (num2 != num3 && count >= 1)) && num3 >= num2) {
+                    result.add(List.of(num1, num2, num3));
+                }
+            }
+
+            counter.remove(num1);
+        }
+
+        return result;
+    }
+}