diff --git a/solutions/125.Valid Palindrome/Solution.java b/solutions/125.Valid Palindrome/Solution.java
index 77349e7..db04b6f 100644
--- a/solutions/125.Valid Palindrome/Solution.java	
+++ b/solutions/125.Valid Palindrome/Solution.java	
@@ -3,7 +3,8 @@ public boolean isPalindrome(String s) {
         s = s.toLowerCase().replaceAll("[^a-z0-9]", "");
         int i = 0, j = s.length() - 1;
         while (i < j) {
-            if (s.charAt(i++) != s.charAt(j--)) return false;
+            if (s.charAt(i++) != s.charAt(j--))
+                return false;
         }
         return true;
     }
diff --git a/solutions/128. Longest Consecutive Sequence/Solution.java b/solutions/128. Longest Consecutive Sequence/Solution.java
index 84dddc0..453742c 100644
--- a/solutions/128. Longest Consecutive Sequence/Solution.java	
+++ b/solutions/128. Longest Consecutive Sequence/Solution.java	
@@ -1,3 +1,5 @@
+import java.util.*;
+
 class Solution {
     public int longestConsecutive(int[] nums) {
         Set<Integer> numSet = new HashSet<>();
diff --git a/solutions/15. 3Sum/Solution.java b/solutions/15. 3Sum/Solution.java
index 30cd09b..bafb16a 100644
--- a/solutions/15. 3Sum/Solution.java	
+++ b/solutions/15. 3Sum/Solution.java	
@@ -1,3 +1,5 @@
+import java.util.*;
+
 class Solution {
     public List<List<Integer>> threeSum(int[] nums) {
         List<List<Integer>> res = new ArrayList<>();
diff --git a/solutions/15. 3Sum/Solution.py b/solutions/15. 3Sum/Solution.py
index 3c38e24..e64633d 100644
--- a/solutions/15. 3Sum/Solution.py	
+++ b/solutions/15. 3Sum/Solution.py	
@@ -4,22 +4,22 @@ def threeSum(self, nums: list[int]) -> list[list[int]]:
         n = len(nums)
         returnList = []
         for i, i_num in enumerate(nums):
-            if i and i_num == nums[i-1]:
+            if i and i_num == nums[i - 1]:
                 continue
-            l = i + 1
-            r = n - 1
-            while l < r:
-                sum = i_num + nums[l] + nums[r]
+            left = i + 1
+            right = n - 1
+            while left < right:
+                sum = i_num + nums[left] + nums[right]
                 if sum == 0:
-                    returnList.append([i_num, nums[l], nums[r]])
-                    while l < r and nums[l] == nums[l+1]:
-                        l += 1
-                    while l < r and nums[r] == nums[r-1]:
-                        r -= 1
-                    l += 1
-                    r -= 1
+                    returnList.append([i_num, nums[left], nums[right]])
+                    while left < right and nums[left] == nums[left + 1]:
+                        left += 1
+                    while left < right and nums[right] == nums[right - 1]:
+                        right -= 1
+                    left += 1
+                    right -= 1
                 elif sum < 0:
-                    l += 1
+                    left += 1
                 else:
-                    r -= 1
+                    right -= 1
         return returnList
diff --git a/solutions/167. Two Integer Sum II/Solution.java b/solutions/167. Two Integer Sum II/Solution.java
index d350c61..95c19db 100644
--- a/solutions/167. Two Integer Sum II/Solution.java	
+++ b/solutions/167. Two Integer Sum II/Solution.java	
@@ -5,7 +5,7 @@ public int[] twoSum(int[] numbers, int target) {
         while (left < right) {
             int sum = numbers[left] + numbers[right];
             if (sum == target) {
-                return new int[] {left + 1, right + 1};
+                return new int[] { left + 1, right + 1 };
             } else if (sum < target) {
                 left++;
             } else {
@@ -13,6 +13,6 @@ public int[] twoSum(int[] numbers, int target) {
             }
         }
 
-        return result;
+        return new int[] { -1, -1 };
     }
 }
diff --git a/solutions/20. Valid Parentheses/Solution.java b/solutions/20. Valid Parentheses/Solution.java
index 06b6439..7e6359d 100644
--- a/solutions/20. Valid Parentheses/Solution.java	
+++ b/solutions/20. Valid Parentheses/Solution.java	
@@ -1,4 +1,4 @@
-import java.util.Stack;
+import java.util.*;
 
 class Solution {
     public boolean isValid(String s) {