LeetCode

• LeetCode solutions in Kotlin

Solved Problems

#	Title	Solution
1	Two Sum	Solution
2	Add Two Numbers	Solution
3	Longest Substring Without Repeating Characters	Solution
4	Median of Two Sorted Arrays	Solution
5	Longest Palindromic Substring	Solution
6	Zigzag Conversion	Solution
7	Reverse Integer	Solution
8	String to Integer (atoi)	Solution
11	Container With Most Water	Solution
12	Integer to Roman	Solution
13	Roman to Integer	Solution
14	Longest Common Prefix	Solution
15	3Sum	Solution
16	3Sum Closest	Solution
17	Letter Combinations of a Phone Number	Solution
18	4Sum	Solution
19	Remove Nth Node From End of List	Solution
20	Valid Parentheses	Solution
21	Merge Two Sorted Lists	Solution
22	Generate Parentheses	Solution
23	Merge k Sorted Lists	Solution
24	Swap Nodes in Pairs	Solution
25	Reverse Nodes in k-Group	Solution
26	Remove Duplicates from Sorted Array	Solution
27	Remove Element	Solution
28	Implement strStr()	Solution
29	Divide Two Integers	Solution
31	Next Permutation	Solution
33	Search in Rotated Sorted Array	Solution
34	Find First and Last Position of Element in Sorted Array	Solution
35	Search Insert Position	Solution
36	Valid Sudoku	Solution
37	Sudoku Solver	Solution
38	Count and Say	Solution
39	Combination Sum	Solution
40	Combination Sum II	Solution
42	Trapping Rain Water	Solution
43	Multiply Strings	Solution
45	Jump Game II	Solution
46	Permutations	Solution
47	Permutations II	Solution
48	Rotate Image	Solution
49	Group Anagrams	Solution
50	Pow(x, n)	Solution
51	N-Queens	Solution
52	N-Queens II	Solution
53	Maximum Subarray	Solution
55	Jump Game	Solution
58	Length of Last Word	Solution
59	Spiral Matrix II	Solution
62	Unique Paths	Solution
63	Unique Paths II	Solution
66	Plus One	Solution
68	Text Justification	Solution
69	Sqrt(x)	Solution
70	Climbing Stairs	Solution
71	Simplify Path	Solution
72	Edit Distance	Solution
73	Set Matrix Zeroes	Solution
75	Sort Colors	Solution
76	Minimum Window Substring	Solution
78	Subsets	Solution
79	Word Search	Solution
80	Remove Duplicates from Sorted Array II	Solution
88	Merge Sorted Array	Solution
94	Binary Tree Inorder Traversal	Solution
100	Same Tree	Solution
101	Symmetric Tree	Solution
102	Binary Tree Level Order Traversal	Solution
104	Maximum Depth of Binary Tree	Solution
108	Convert Sorted Array to Binary Search Tree	Solution
111	Minimum Depth of Binary Tree	Solution
118	Pascal's Triangle	Solution
120	Triangle	Solution
121	Best Time to Buy and Sell Stock	Solution
122	Best Time to Buy and Sell Stock II	Solution
125	Valid Palindrome	Solution
131	Palindrome Partitioning	Solution
133	Clone Graph	Solution
134	Gas Station	Solution
135	Candy	Solution
136	Single Number	Solution
139	Word Break	Solution
141	Linked List Cycle	Solution
143	Reorder List	Solution
149	Max Points on a Line	Solution
150	Evaluate Reverse Polish Notation	Solution
151	Reverse Words in a String	Solution
155	Min Stack	Solution
160	Intersection of Two Linked Lists	Solution
162	Find Peak Element	Solution
165	Compare Version Numbers	Solution
167	Two Sum II - Input Array Is Sorted	Solution
169	Majority Element	Solution
171	Excel Sheet Column Number	Solution
172	Factorial Trailing Zeroes	Solution
179	Largest Number	Solution
189	Rotate Array	Solution
190	Reverse Bits	Solution
191	Number of 1 Bits	Solution
198	House Robber	Solution
199	Binary Tree Right Side View	Solution
200	Number of Islands	Solution
201	Bitwise AND of Numbers Range	Solution
202	Happy Number	Solution
204	Count Primes	Solution
206	Reverse Linked List	Solution
208	Implement Trie (Prefix Tree)	Solution
209	Minimum Size Subarray Sum	Solution
215	Kth Largest Element in an Array	Solution
216	Combination Sum III	Solution
217	Contains Duplicate	Solution
219	Contains Duplicate II	Solution
225	Implement Stack using Queues	Solution
230	Kth Smallest Element in a BST	Solution
231	Power of Two	Solution
232	Implement Queue using Stacks	Solution
234	Palindrome Linked List	Solution
236	Lowest Common Ancestor of a Binary Tree	Solution
237	Delete Node in a Linked List	Solution
238	Product of Array Except Self	Solution
240	Search a 2D Matrix II	Solution
241	Different Ways to Add Parentheses	Solution
242	Valid Anagram	Solution
260	Single Number III	Solution
268	Missing Number	Solution
273	Integer to English Words	Solution
274	H-Index	Solution
279	Perfect Squares	Solution
283	Move Zeroes	Solution
287	Find the Duplicate Number	Solution
289	Game of Life	Solution
304	Range Sum Query 2D - Immutable	Solution
310	Minimum Height Trees	Solution
318	Maximum Product of Word Lengths	Solution
322	Coin Change	Solution
326	Power of Three	Solution
328	Odd Even Linked List	Solution
329	Longest Increasing Path in a Matrix	Solution
334	Increasing Triplet Subsequence	Solution
338	Counting Bits	Solution
344	Reverse String	Solution
345	Reverse Vowels of a String	Solution
347	Top K Frequent Elements	Solution
349	Intersection of Two Arrays	Solution
350	Intersection of Two Arrays II	Solution
350	Intersection of Two Arrays II	Solution
368	Largest Divisible Subset	Solution
371	Sum of Two Integers	Solution
374	Guess Number Higher or Lower	Solution
377	Combination Sum IV	Solution
378	Kth Smallest Element in a Sorted Matrix	Solution
380	Insert Delete GetRandom O(1)	Solution
381	Insert Delete GetRandom O(1) - Duplicates allowed	Solution
386	Lexicographical Numbers	Solution
387	First Unique Character in a String	Solution
392	Is Subsequence	Solution
394	Decode String	Solution
399	Evaluate Division	Solution
409	Longest Palindrome	Solution
412	Fizz Buzz	Solution
416	Partition Equal Subset Sum	Solution
435	Non-overlapping Intervals	Solution
437	Path Sum III	Solution
440	K-th Smallest in Lexicographical Order	Solution
442	Find All Duplicates in an Array	Solution
443	String Compression	Solution
450	Delete Node in a BST	Solution
451	Sort Characters By Frequency	Solution
452	Minimum Number of Arrows to Burst Balloons	Solution
456	132 Pattern	Solution
463	Island Perimeter	Solution
474	Ones and Zeroes	Solution
476	Number Complement	Solution
495	Teemo Attacking	Solution
506	Relative Ranks	Solution
513	Find Bottom Left Tree Value	Solution
514	Freedom Trail	Solution
523	Continuous Subarray Sum	Solution
535	Encode and Decode TinyURL	Solution
539	Minimum Time Difference	Solution
543	Diameter of Binary Tree	Solution
547	Number of Provinces	Solution
581	Shortest Unsorted Continuous Subarray	Solution
583	Delete Operation for Two Strings	Solution
590	N-ary Tree Postorder Traversal	Solution
592	Fraction Addition and Subtraction	Solution
605	Can Place Flowers	Solution
633	Sum of Square Numbers	Solution
641	Design Circular Deque	Solution
643	Maximum Average Subarray I	Solution
645	Set Mismatch	Solution
647	Palindromic Substrings	Solution
648	Replace Words	Solution
649	Dota2 Senate	Solution
664	Strange Printer	Solution
667	Beautiful Arrangement II	Solution
678	Valid Parenthesis String	Solution
682	Baseball Game	Solution
700	Search in a Binary Search Tree	Solution
706	Design HashMap	Solution
713	Subarray Product Less Than K	Solution
714	Best Time to Buy and Sell Stock with Transaction Fee	Solution
719	Find K-th Smallest Pair Distance	Solution
724	Find Pivot Index	Solution
725	Split Linked List in Parts	Solution
729	My Calendar I	Solution
735	Asteroid Collision	Solution
739	Daily Temperatures	Solution
743	Network Delay Time	Solution
746	Min Cost Climbing Stairs	Solution
752	Open the Lock	Solution
773	Sliding Puzzle	Solution
777	Swap Adjacent in LR String	Solution
781	Rabbits in Forest	Solution
786	K-th Smallest Prime Fraction	Solution
790	Domino and Tromino Tiling	Solution
791	Custom Sort String	Solution
796	Rotate String	Solution
802	Find Eventual Safe States	Solution
826	Most Profit Assigning Work	Solution
827	Making A Large Island	Solution
840	Magic Squares In Grid	Solution
841	Keys and Rooms	Solution
844	Backspace String Compare	Solution
846	Hand of Straights	Solution
858	Mirror Reflection	Solution
862	Shortest Subarray with Sum at Least K	Solution
865	Smallest Subtree with all the Deepest Nodes	Solution
872	Leaf-Similar Trees	Solution
874	Walking Robot Simulation	Solution
875	Koko Eating Bananas	Solution
876	Middle of the Linked List	Solution
881	Boats to Save People	Solution
884	Uncommon Words from Two Sentences	Solution
901	Online Stock Span	Solution
905	Sort Array By Parity	Solution
907	Sum of Subarray Minimums	Solution
914	X of a Kind in a Deck of Cards	Solution
916	Word Subsets	Solution
917	Reverse Only Letters	Solution
921	Minimum Add to Make Parentheses Valid	Solution
933	Number of Recent Calls	Solution
945	Minimum Increment to Make Array Unique	Solution
951	Flip Equivalent Binary Trees	Solution
974	Subarray Sums Divisible by K	Solution
977	Squares of a Sorted Array	Solution
979	Distribute Coins in Binary Tree	Solution
980	Unique Paths III	Solution
983	Minimum Cost For Tickets	Solution
994	Rotting Oranges	Solution
995	Minimum Number of K Consecutive Bit Flips	Solution
997	Find the Town Judge	Solution
1002	Find Common Characters	Solution
1004	Max Consecutive Ones III	Solution
1038	Binary Search Tree to Greater Sum Tree	Solution
1043	Partition Array for Maximum Sum	Solution
1047	Remove All Adjacent Duplicates In String	Solution
1048	Longest String Chain	Solution
1051	Height Checker	Solution
1052	Grumpy Bookstore Owner	Solution
1071	Greatest Common Divisor of Strings	Solution
1079	Letter Tile Possibilities	Solution
1091	Shortest Path in Binary Matrix	Solution
1105	Filling Bookcase Shelves	Solution
1106	Parsing A Boolean Expression	Solution
1122	Relative Sort Array	Solution
1123	Lowest Common Ancestor of Deepest Leaves	Solution
1137	N-th Tribonacci Number	Solution
1143	Longest Common Subsequence	Solution
1161	Maximum Level Sum of a Binary Tree	Solution
1171	Remove Zero Sum Consecutive Nodes from Linked List	Solution
1202	Smallest String With Swaps	Solution
1207	Unique Number of Occurrences	Solution
1208	Get Equal Substrings Within Budget	Solution
1209	Remove All Adjacent Duplicates in String II	Solution
1219	Path with Maximum Gold	Solution
1248	Count Number of Nice Subarrays	Solution
1249	Minimum Remove to Make Valid Parentheses	Solution
1260	Shift 2D Grid	Solution
1267	Count Servers that Communicate	Solution
1268	Search Suggestions System	Solution
1277	Count Square Submatrices with All Ones	Solution
1289	Minimum Falling Path Sum II	Solution
1291	Sequential Digits	Solution
1293	Shortest Path in a Grid with Obstacles Elimination	Solution
1295	Find Numbers with Even Number of Digits	Solution
1302	Deepest Leaves Sum	Solution
1310	XOR Queries of a Subarray	Solution
1318	Minimum Flips to Make a OR b Equal to c	Solution
1331	Rank Transform of an Array	Solution
1346	Check If N and Its Double Exist	Solution
1352	Product of the Last K Numbers	Solution
1356	Sort Integers by The Number of 1 Bits	Solution
1358	Number of Substrings Containing All Three Characters	Solution
1367	Linked List in Binary Tree	Solution
1372	Longest ZigZag Path in a Binary Tree	Solution
1380	Lucky Numbers in a Matrix	Solution
1381	Design a Stack With Increment Operation	Solution
1382	Balance a Binary Search Tree	Solution
1395	Count Number of Teams	Solution
1399	Count Largest Group	Solution
1400	Construct K Palindrome Strings	Solution
1404	Number of Steps to Reduce a Number in Binary Representation to One	Solution
1405	Longest Happy String	Solution
1408	String Matching in an Array	Solution
1415	The k-th Lexicographical String of All Happy Strings of Length n	Solution
1422	Maximum Score After Splitting a String	Solution
1431	Kids With the Greatest Number of Candies	Solution
1438	Longest Continuous Subarray With Absolute Diff Less Than or Equal to Limit	Solution
1448	Count Good Nodes in Binary Tree	Solution
1450	Number of Students Doing Homework at a Given Time	Solution
1455	Check If a Word Occurs As a Prefix of Any Word in a Sentence	Solution
1456	Maximum Number of Vowels in a Substring of Given Length	Solution
1463	Cherry Pickup II	Solution
1466	Reorder Routes to Make All Paths Lead to the City Zero	Solution
1480	Running Sum of 1d Array	Solution
1481	Least Number of Unique Integers after K Removals	Solution
1482	Minimum Number of Days to Make m Bouquets	Solution
1493	Longest Subarray of 1's After Deleting One Element	Solution
1497	Check If Array Pairs Are Divisible by k	Solution
1509	Minimum Difference Between Largest and Smallest Value in Three Moves	Solution
1514	Path with Maximum Probability	Solution
1518	Water Bottles	Solution
1524	Number of Sub-arrays With Odd Sum	Solution
1530	Number of Good Leaf Nodes Pairs	Solution
1534	Count Good Triplets	Solution
1545	Find Kth Bit in Nth Binary String	Solution
1550	Three Consecutive Odds	Solution
1574	Shortest Subarray to be Removed to Make Array Sorted	Solution
1590	Make Sum Divisible by P	Solution
1593	Split a String Into the Max Number of Unique Substrings	Solution
1598	Crawler Log Folder	Solution
1608	Special Array With X Elements Greater Than or Equal X	Solution
1626	Best Team With No Conflicts	Solution
1636	Sort Array by Increasing Frequency	Solution
1642	Furthest Building You Can Reach	Solution
1652	Defuse the Bomb	Solution
1653	Minimum Deletions to Make String Balanced	Solution
1657	Determine if Two Strings Are Close	Solution
1658	Minimum Operations to Reduce X to Zero	Solution
1669	Merge In Between Linked Lists	Solution
1679	Max Number of K-Sum Pairs	Solution
1684	Count the Number of Consistent Strings	Solution
1695	Maximum Erasure Value	Solution
1700	Number of Students Unable to Eat Lunch	Solution
1701	Average Waiting Time	Solution
1718	Construct the Lexicographically Largest Valid Sequence	Solution
1726	Tuple with Same Product	Solution
1732	Find the Highest Altitude	Solution
1750	Minimum Length of String After Deleting Similar Ends	Solution
1752	Check if Array Is Sorted and Rotated	Solution
1758	Minimum Changes To Make Alternating Binary String	Solution
1765	Map of Highest Peak	Solution
1768	Merge Strings Alternately	Solution
1769	Minimum Number of Operations to Move All Balls to Each Box	Solution
1780	Check if Number is a Sum of Powers of Three	Solution
1790	Check if One String Swap Can Make Strings Equal	Solution
1791	Find Center of Star Graph	Solution
1800	Maximum Ascending Subarray Sum	Solution
1823	Find the Winner of the Circular Game	Solution
1829	Maximum XOR for Each Query	Solution
1863	Sum of All Subset XOR Totals	Solution
1882	Process Tasks Using Servers	Solution
1894	Find the Student that Will Replace the Chalk	Solution
1905	Count Sub Islands	Solution
1906	Minimum Absolute Difference Queries	Solution
1910	Remove All Occurrences of a Substring	Solution
1915	Number of Wonderful Substrings	Solution
1922	Count Good Numbers	Solution
1926	Nearest Exit from Entrance in Maze	Solution
1930	Unique Length-3 Palindromic Subsequences	Solution
1945	Sum of Digits of String After Convert	Solution
1957	Delete Characters to Make Fancy String	Solution
1963	Minimum Number of Swaps to Make the String Balanced	Solution
1971	Find if Path Exists in Graph	Solution
1980	Find Unique Binary String	Solution
1992	Find All Groups of Farmland	Solution
2000	Reverse Prefix of Word	Solution
2016	Maximum Difference Between Increasing Elements	Solution
2017	Grid Game	Solution
2022	Convert 1D Array Into 2D Array	Solution
2024	Maximize the Confusion of an Exam	Solution
2028	Find Missing Observations	Solution
2037	Minimum Number of Moves to Seat Everyone	Solution
2044	Count Number of Maximum Bitwise-OR Subsets	Solution
2053	Kth Distinct String in an Array	Solution
2070	Most Beautiful Item for Each Query	Solution
2073	Time Needed to Buy Tickets	Solution
2090	K Radius Subarray Averages	Solution
2095	Delete the Middle Node of a Linked List	Solution
2108	Find First Palindromic String in the Array	Solution
2109	Adding Spaces to a String	Solution
2115	Find All Possible Recipes from Given Supplies	Solution
2116	Check if a Parentheses String Can Be Valid	Solution
2130	Maximum Twin Sum of a Linked List	Solution
2131	Longest Palindrome by Concatenating Two Letter Words	Solution
2133	Check if Every Row and Column Contains All Numbers	Solution
2140	Solving Questions With Brainpower	Solution
2145	Count the Hidden Sequences	Solution
2149	Rearrange Array Elements by Sign	Solution
2161	Partition Array According to Given Pivot	Solution
2176	Count Equal and Divisible Pairs in an Array	Solution
2179	Count Good Triplets in an Array	Solution
2181	Merge Nodes in Between Zeros	Solution
2185	Counting Words With a Given Prefix	Solution
2186	Minimum Number of Steps to Make Two Strings Anagram II	Solution
2192	All Ancestors of a Node in a Directed Acyclic Graph	Solution
2206	Divide Array Into Equal Pairs	Solution
2215	Find the Difference of Two Arrays	Solution
2220	Minimum Bit Flips to Convert Number	Solution
2257	Count Unguarded Cells in the Grid	Solution
2270	Number of Ways to Split Array	Solution
2275	Largest Combination With Bitwise AND Greater Than Zero	Solution
2285	Maximum Total Importance of Roads	Solution
2290	Minimum Obstacle Removal to Reach Corner	Solution
2300	Successful Pairs of Spells and Potions	Solution
2309	Greatest English Letter in Upper and Lower Case	Solution
2326	Spiral Matrix IV	Solution
2336	Smallest Number in Infinite Set	Solution
2337	Move Pieces to Obtain a String	Solution
2338	Count the Number of Ideal Arrays	Solution
2342	Max Sum of a Pair With Equal Sum of Digits	Solution
2349	Design a Number Container System	Solution
2352	Equal Row and Column Pairs	Solution
2364	Count Number of Bad Pairs	Solution
2373	Largest Local Values in a Matrix	Solution
2375	Construct Smallest Number From DI String	Solution
2379	Minimum Recolors to Get K Consecutive Black Blocks	Solution
2381	Shifting Letters II	Solution
2390	Removing Stars From a String	Solution
2401	Longest Nice Subarray	Solution
2402	Meeting Rooms III	Solution
2406	Divide Intervals Into Minimum Number of Groups	Solution
2416	Sum of Prefix Scores of Strings	Solution
2418	Sort the People	Solution
2419	Longest Subarray With Maximum Bitwise AND	Solution
2425	Bitwise XOR of All Pairings	Solution
2427	Number of Common Factors	Solution
2429	Minimize XOR	Solution
2441	Largest Positive Integer That Exists With Its Negative	Solution
2451	Odd String Difference	Solution
2460	Apply Operations to an Array	Solution
2461	Maximum Sum of Distinct Subarrays With Length K	Solution
2462	Total Cost to Hire K Workers	Solution
2485	Find the Pivot Integer	Solution
2486	Append Characters to String to Make Subsequence	Solution
2487	Remove Nodes From Linked List	Solution
2490	Circular Sentence	Solution
2491	Divide Players Into Teams of Equal Skill	Solution
2501	Longest Square Streak in an Array	Solution
2503	Maximum Number of Points From Grid Queries	Solution
2523	Closest Prime Numbers in Range	Solution
2527	Find Xor-Beauty of Array	Solution
2529	Maximum Count of Positive Integer and Negative Integer	Solution
2530	Maximal Score After Applying K Operations	Solution
2537	Count the Number of Good Subarrays	Solution
2540	Minimum Common Value	Solution
2542	Maximum Subsequence Score	Solution
2554	Maximum Number of Integers to Choose From a Range I	Solution
2558	Take Gifts From the Richest Pile	Solution
2559	Count Vowel Strings in Ranges	Solution
2563	Count the Number of Fair Pairs	Solution
2570	Merge Two 2D Arrays by Summing Values	Solution
2577	Minimum Time to Visit a Cell In a Grid	Solution
2579	Count Total Number of Colored Cells	Solution
2582	Pass the Pillow	Solution
2583	Kth Largest Sum in a Binary Tree	Solution
2587	Rearrange Array to Maximize Prefix Score	Solution
2597	The Number of Beautiful Subsets	Solution
2601	Prime Subtraction Operation	Solution
2657	Find the Prefix Common Array of Two Arrays	Solution
2658	Maximum Number of Fish in a Grid	Solution
2661	First Completely Painted Row or Column	Solution
2678	Number of Senior Citizens	Solution
2684	Maximum Number of Moves in a Grid	Solution
2707	Extra Characters in a String	Solution
2788	Split Strings by Separator	Solution
2799	Count Complete Subarrays in an Array	Solution
2807	Insert Greatest Common Divisors in Linked List	Solution
2816	Double a Number Represented as a Linked List	Solution
2825	Make String a Subsequence Using Cyclic Increments	Solution
2843	Count Symmetric Integers	Solution
2845	Count of Interesting Subarrays	Solution
2864	Maximum Odd Binary Number	Solution
2873	Maximum Value of an Ordered Triplet I	Solution
2874	Maximum Value of an Ordered Triplet II	Solution
2894	Divisible and Non-divisible Sums Difference	Solution
2914	Minimum Number of Changes to Make Binary String Beautiful	Solution
2924	Find Champion II	Solution
2929	Distribute Candies Among Children II	Solution
2938	Separate Black and White Balls	Solution
2942	Find Words Containing Character	Solution
2965	Find Missing and Repeated Values	Solution
2971	Find Polygon With the Largest Perimeter	Solution
2996	Smallest Missing Integer Greater Than Sequential Prefix Sum	Solution
2997	Minimum Number of Operations to Make Array XOR Equal to K	Solution
3005	Count Elements With Maximum Frequency	Solution
3011	Find if Array Can Be Sorted	Solution
3042	Count Prefix and Suffix Pairs I	Solution
3066	Minimum Operations to Exceed Threshold Value II	Solution
3069	Distribute Elements Into Two Arrays I	Solution
3071	Minimum Operations to Write the Letter Y on a Grid	Solution
3075	Maximize Happiness of Selected Children	Solution
3083	Existence of a Substring in a String and Its Reverse	Solution
3105	Longest Strictly Increasing or Strictly Decreasing Subarray	Solution
3110	Score of a String	Solution
3151	Special Array I	Solution
3160	Find the Number of Distinct Colors Among the Balls	Solution
3163	String Compression III	Solution
3169	Count Days Without Meetings	Solution
3170	Lexicographically Minimum String After Removing Stars	Solution
3174	Clear Digits	Solution
3191	Minimum Operations to Make Binary Array Elements Equal to One I	Solution
3217	Delete Nodes From Linked List Present in Array	Solution
3223	Minimum Length of String After Operations	Solution
3243	Shortest Distance After Road Addition Queries I	Solution
3306	Count of Substrings Containing Every Vowel and K Consonants II	Solution
3334	Find the Maximum Factor Score of Array	Solution
3335	Total Characters in String After Transformations I	Solution
3337	Total Characters in String After Transformations II	Solution
3340	Check Balanced String	Solution
3341	Find Minimum Time to Reach Last Room I	Solution
3375	Minimum Operations to Make Array Values Equal to K	Solution
3394	Check if Grid can be Cut into Sections	Solution
3396	Minimum Number of Operations to Make Elements in Array Distinct	Solution
3423	Maximum Difference Between Adjacent Elements in a Circular Array	Solution
3442	Maximum Difference Between Even and Odd Frequency I	Solution
3507	Minimum Pair Removal to Sort Array I	Solution
3508	Implement Router	Solution