update 15

Author: fishercoder1534

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

@@ -5,37 +5,36 @@
 import java.util.List;
 
 public class _15 {
-
     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]) {
+            for (int left = 0; left < nums.length - 2; left++) {
+                if (left >= 1 && nums[left] == nums[left - 1]) {
                     continue;
                 }
-                int left = i + 1;
+                int mid = left + 1;
                 int right = nums.length - 1;
-                while (left < right) {
-                    int sum = nums[i] + nums[left] + nums[right];
+                while (mid < right) {
+                    int sum = nums[left] + nums[mid] + nums[right];
                     if (sum == 0) {
-                        result.add(Arrays.asList(nums[i], nums[left], nums[right]));
+                        result.add(Arrays.asList(nums[left], nums[mid], nums[right]));
 
-                        while (left < right && nums[left] == nums[left + 1]) {
-                            left++;
+                        while (mid < right && nums[mid] == nums[mid + 1]) {
+                            mid++;
                         }
 
-                        while (left < right && nums[right] == nums[right - 1]) {
+                        while (mid < right && nums[right] == nums[right - 1]) {
                             right--;
                         }
                         //these two lines are critical and easy to forget, if so, it'll TLE
-                        left++;
+                        mid++;
                         right--;
                     } else if (sum > 0) {
                         right--;
                     } else {
-                        left++;
+                        mid++;
                     }
                 }
             }

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

@@ -29,4 +29,11 @@ public void test1() {
         assertEquals(expected, solution1.threeSum(nums));
     }
 
+    @Test
+    public void test2() {
+        nums = new int[]{1, 2, -2, -1};
+        expected = new ArrayList<>();
+        assertEquals(expected, solution1.threeSum(nums));
+    }
+
 }