refactor 15

Author: fishercoder1534

src/main/java/com/fishercoder/solutions/_15.java

@@ -6,10 +6,11 @@
 
 /**
  * 15. 3Sum
+ *
  * Given an array S of n integers, are there elements a, b, c in S such that a + b + c = 0?
  * Find all unique triplets in the array which gives the sum of zero.
-
- Note: The solution set must not contain duplicate triplets.
+ *
+ * Note: The solution set must not contain duplicate triplets.
 
  For example, given array S = [-1, 0, 1, 2, -1, -4],
 
@@ -22,39 +23,38 @@
 
 public class _15 {
 
-    public List<List<Integer>> threeSum(int[] nums) {
-        List<List<Integer>> result = new ArrayList<>();
-        if (nums == null || nums.length == 0) {
-            return result;
-        }
-
-        Arrays.sort(nums);
-        for (int i = 0; i < nums.length; i++) {
-            if (i >= 1 && nums[i] == nums[i - 1]) {
-                continue;
-            }
-            int left = i + 1;
-            int right = nums.length - 1;
-            while (left < right) {
-                int sum = nums[i] + nums[left] + nums[right];
-                if (sum == 0) {
-                    result.add(Arrays.asList(nums[i], nums[left], nums[right]));
-                    /**be sure to skip duplicates*/
-                    while (left + 1 < right && nums[left] == nums[left + 1]) {
+    public static class Solution1 {
+        public List<List<Integer>> threeSum(int[] nums) {
+            Arrays.sort(nums);
+            List<List<Integer>> result = new ArrayList<>();
+            for (int i = 0; i < nums.length - 2; i++) {
+                if (i >= 1 && nums[i] == nums[i - 1]) {
+                    continue;
+                }
+                int left = i + 1;
+                int right = nums.length - 1;
+                while (left < right) {
+                    int sum = nums[i] + nums[left] + nums[right];
+                    if (sum == 0) {
+                        result.add(Arrays.asList(nums[i], nums[left], nums[right]));
+
+                        while (left + 1 < right && nums[left] == nums[left + 1]) {
+                            left++;
+                        }
+
+                        while (right - 1 > left && nums[right] == nums[right - 1]) {
+                            right--;
+                        }
                         left++;
-                    }
-                    while (right - 1 > left && nums[right] == nums[right - 1]) {
                         right--;
+                    } else if (sum > 0) {
+                        right--;
+                    } else {
+                        left++;
                     }
-                    left++;
-                    right--;
-                } else if (sum > 0) {
-                    right--;
-                } else {
-                    left++;
                 }
             }
+            return result;
         }
-        return result;
     }
 }

src/test/java/com/fishercoder/_15Test.java

@@ -0,0 +1,32 @@
+package com.fishercoder;
+
+import com.fishercoder.solutions._15;
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+
+import static org.junit.Assert.assertEquals;
+
+public class _15Test {
+    private static _15.Solution1 solution1;
+    private static int[] nums;
+    private static List<List<Integer>> expected;
+
+    @BeforeClass
+    public static void setup() {
+        solution1 = new _15.Solution1();
+    }
+
+    @Test
+    public void test1() {
+        nums = new int[]{-1, 0, 1, 2, -1, -4};
+        expected = new ArrayList<>();
+        expected.add(Arrays.asList(-1, -1, 2));
+        expected.add(Arrays.asList(-1, 0, 1));
+        assertEquals(expected, solution1.threeSum(nums));
+    }
+
+}