fix: add missing newlines at end of files

Author: DaleSeo

binary-tree-level-order-traversal/WhiteHyun.swift

@@ -104,4 +104,4 @@ class Solution {
 
     return array
   }
-}
+}

contains-duplicate/TonyKim9401.java

@@ -14,4 +14,4 @@ public boolean containsDuplicate(int[] nums) {
         }
         return false;
     }
-}
+}

kth-smallest-element-in-a-bst/TonyKim9401.java

@@ -15,4 +15,4 @@ public void visitTreeNode(TreeNode node) {
     }
     // time complexity: O(n), visit all nodes once
     // space complexity: O(1), used an array list
-}
+}

number-of-1-bits/TonyKim9401.java

@@ -18,4 +18,4 @@ public int hammingWeight(int n) {
         return output;
         */
     }
-}
+}

number-of-connected-components-in-an-undirected-graph/WhiteHyun.swift

@@ -37,4 +37,4 @@ final class Solution {
 
     return count
   }
-}
+}

palindromic-substrings/TonyKim9401.java

@@ -49,4 +49,4 @@ public boolean palindromic(String candidate) {
         }
         return true;
     }
-}
+}

top-k-frequent-elements/TonyKim9401.java

@@ -29,4 +29,4 @@ public int[] topKFrequent(int[] nums, int k) {
 
         return output;
     }
-}
+}