Amazon

2015 problems

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Problem	Difficulty	Frequency	Topics
2148. Count Elements With Strictly Smaller and Greater Elements	Easy	5%	ArraySortingCounting
3399. Smallest Substring With Identical Characters II	Hard	5%	StringBinary Search
2202. Maximize the Topmost Element After K Moves	Medium	5%	ArrayGreedy
1239. Maximum Length of a Concatenated String with Unique Characters	Medium	5%	ArrayStringBacktrackingBit Manipulation
2091. Removing Minimum and Maximum From Array	Medium	5%	ArrayGreedy
1051. Height Checker	Easy	5%	ArraySortingCounting SortBubble Sort
2442. Count Number of Distinct Integers After Reverse Operations	Medium	5%	ArrayHash TableMathCounting
2785. Sort Vowels in a String	Medium	5%	StringSorting
1330. Reverse Subarray To Maximize Array Value	Hard	5%	ArrayMathGreedy
3871. Count Commas in Range II	Medium	5%	Math
1105. Filling Bookcase Shelves	Medium	5%	ArrayDynamic Programming
Shortest Path in a Hidden Grid	Medium	5%	ArrayDepth-First SearchBreadth-First SearchMatrixInteractive
4046. Minimum Cost Path With At Most K Turns	Hard	5%	ArrayHeapGraph TheoryMatrixShortest Path
The Latest Login in 2020	Easy	5%	Database
Array Reduce Transformation	Easy	5%	—
3271. Hash Divided String	Medium	5%	StringSimulation
1801. Number of Orders in the Backlog	Medium	5%	ArrayHeap (Priority Queue)Simulation
3248. Snake in Matrix	Easy	5%	ArrayStringSimulation
Employees Whose Manager Left the Company	Easy	5%	Database
766. Toeplitz Matrix	Easy	5%	ArrayMatrix
4066. Maximum Equal Adjacent Pairs After at Most One Replacement	Medium	5%	ArrayHash TableCounting
3878. Count Good Subarrays	Hard	5%	ArrayStackBit ManipulationMonotonic Stack
Linked List Random Node	Medium	5%	Linked ListMathReservoir SamplingRandomized
3159. Find Occurrences of an Element in an Array	Medium	5%	ArrayHash Table
Building H2O	Medium	5%	Concurrency