3Sum

Author: TonyKim9401

3sum/TonyKim9401.java

@@ -0,0 +1,30 @@
+// TC: O(n^2)
+// SC: O(n)
+public class Solution {
+    public List<List<Integer>> threeSum(int[] nums) {
+
+        Arrays.sort(nums);
+
+        List<List<Integer>> output = new ArrayList<>();
+        Map<Integer, Integer> map = new HashMap<>();
+
+        for (int i = 0; i < nums.length; ++i) map.put(nums[i], i);
+
+        for (int i = 0; i < nums.length - 2; ++i) {
+            if (nums[i] > 0) break;
+
+            for (int j = i + 1; j < nums.length - 1; ++j) {
+                int cValue = -1 * (nums[i] + nums[j]);
+
+                if (map.containsKey(cValue) && map.get(cValue) > j) {
+                    output.add(List.of(nums[i], nums[j], cValue));
+                }
+                j = map.get(nums[j]);
+            }
+
+            i = map.get(nums[i]);
+        }
+
+        return output;
+    }
+}