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Array
Easy
- Two Sum
- Best Time to Buy and Sell Stock
- Unique Number of Occurrences
- Merge Sorted Array
- Contains Duplicate
- Pascal’s Triangle
- Sort Integers by The Number of 1 Bits
- Running Sum of 1d Array
- Remove Duplicates from Sorted Array
- Move Zeroes
- Check If It Is a Straight Line
- Binary Search
- Majority Element
- Richest Customer Wealth
- Intersection of Two Arrays
- Flood Fill
Medium
- Predict the Winner
- Spiral Matrix
- 3Sum
- Merge Intervals
- Number of Islands
- Next Permutation
- Container With Most Water
- Maximum Subarray
- Minimize Maximum of Array
- Group Anagrams
- Subarray Sum Equals K
- Kth Largest Element in an Array
- Rotate Image
- Longest Consecutive Sequence
- Shortest Bridge
- Fair Distribution of Cookies
- Search in Rotated Sorted Array
- Boats to Save People
Hard
- Trapping Rain Water
- Median of Two Sorted Arrays
- Minimum Number of Taps to Open to Water a Garden
- Frog Jump
- Minimum Cost to Make Array Equal
Sorting
Easy
- Merge Sorted Array
- Contains Duplicate
- Sort Integers by The Number of 1 Bits
- Valid Anagram
- Majority Element
- Intersection of Two Arrays
- Can Make Arithmetic Progression From Sequence
- Average Salary Excluding the Minimum and Maximum Salary
- Squares of a Sorted Array
- Sort Array by Increasing Frequency
- Missing Number
- The K Weakest Rows in a Matrix
- Fair Candy Swap
- Maximum Product of Three Numbers
- Intersection of Two Arrays II
- Minimum Absolute Difference
Medium
- 3Sum
- Merge Intervals
- Group Anagrams
- Reorganize String
- Kth Largest Element in an Array
- Boats to Save People
- Least Number of Unique Integers after K Removals
- 4Sum
- Meeting Rooms II ~ Premium
- Top K Frequent Elements
- Largest Number
- Number of Subsequences That Satisfy the Given Sum Condition
- Maximum Length of Pair Chain
- Design a Todo List ~ Premium
- Rank Teams by Votes
Hard
- Minimum Cost to Make Array Equal
- Maximum Number of Events That Can Be Attended II
- Put Marbles in Bags
- Smallest Range Covering Elements from K Lists
Binary Search
Easy
- Binary Search
- Intersection of Two Arrays
- Sqrt(x)
- First Bad Version
- Missing Number
- Search Insert Position
- Count Negative Numbers in a Sorted Matrix
- The K Weakest Rows in a Matrix
- Fair Candy Swap
- Kth Missing Positive Number
- Intersection of Two Arrays II
- Find Smallest Letter Greater Than Target
- Arranging Coins
- Special Array With X Elements Greater Than or Equal X
Medium
- Minimize Maximum of Array
- Maximum Value at a Given Index in a Bounded Array
- Search in Rotated Sorted Array
- Longest Arithmetic Subsequence
- Minimize the Maximum Difference of Pairs
- Longest Increasing Subsequence
- Peak Index in a Mountain Array
- Maximize the Confusion of an Exam
- Capacity To Ship Packages Within D Days
- Koko Eating Bananas
- Number of Subsequences That Satisfy the Given Sum Condition
- Design Hit Counter ~ Premium
- Find the Duplicate Number
- Single Element in a Sorted Array
Hard
- Median of Two Sorted Arrays
- Minimum Cost to Make Array Equal
- Maximum Running Time of N Computers
- Maximum Number of Events That Can Be Attended II
- Partition Array Into Two Arrays to Minimize Sum Difference
- Maximum Profit in Job Scheduling
Hash Table
Easy
- Two Sum
- Roman to Integer
- Unique Number of Occurrences
- Contains Duplicate
- Majority Element
- Valid Anagram
- Happy Number
- Logger Rate Limiter ~ Premium
- Intersection of Two Arrays
- Degree of an Array
- Isomorphic Strings
- Check Whether Two Strings are Almost Equivalent
- Sort Array by Increasing Frequency
- Next Greater Element I
- Missing Number
- Linked List Cycle
- First Unique Character in a String
- Contains Duplicate II
- Buddy Strings
Medium
- Longest Substring Without Repeating Characters
- LRU Cache
- Letter Combinations of a Phone Number
- Line Reflection ~ Premium
- Reorganize String
- Group Anagrams
- Longest Consecutive Sequence
- Longest Arithmetic Subsequence
- Subarray Sum Equals K
- Longest Arithmetic Subsequence of Given Difference
- Set Matrix Zeroes
- Least Number of Unique Integers after K Removals
- Design Authentication Manager