Array Interview Questions

Index-based sequences, scanning, and in-place mutation patterns used in most interviews.

433 problems

#	Title	Difficulty	Topics
26	Remove Duplicates from Sorted Array	Easy	array
27	Remove Element	Easy	array
31	Next Permutation	Medium	array
41	First Missing Positive	Hard	array
48	Rotate Image	Medium	array
54	Spiral Matrix	Medium	array
59	Spiral Matrix II	Medium	array
66	Plus One	Easy	array
73	Set Matrix Zeroes	Medium	array
80	Remove Duplicates from Sorted Array II	Medium	array
118	Pascal's Triangle	Easy	array
119	Pascal's Triangle II	Easy	array
121	Best Time to Buy and Sell Stock	Easy	array
128	Longest Consecutive Sequence	Hard	array
157	Read N Characters Given Read4	Easy	array
158	Read N Characters Given Read4 II - Call multiple times	Hard	array
163	Missing Ranges	Medium	array
169	Majority Element	Easy	array
189	Rotate Array	Easy	array
215	Kth Largest Element in an Array	Medium	array
228	Summary Ranges	Medium	array
229	Majority Element II	Medium	array
238	Product of Array Except Self	Medium	array
240	Search a 2D Matrix II	Medium	array
243	Shortest Word Distance	Easy	array
245	Shortest Word Distance III	Medium	array
251	Flatten 2D Vector	Medium	array
277	Find the Celebrity	Medium	array
289	Game of Life	Medium	array
293	Flip Game	Easy	array
296	Best Meeting Point	Hard	array
311	Sparse Matrix Multiplication	Medium	array
334	Increasing Triplet Subsequence	Medium	array
370	Range Addition	Medium	array
384	Shuffle an Array	Medium	array
396	Rotate Function	Easy	array
412	Fizz Buzz	Easy	array
414	Third Maximum Number	Easy	array
419	Battleships in a Board	Medium	array
422	Valid Word Square	Easy	array
442	Find All Duplicates in an Array	Medium	array
448	Find All Numbers Disappeared in an Array	Easy	array
462	Minimum Moves to Equal Array Elements II	Medium	array
463	Island Perimeter	Easy	array
485	Max Consecutive Ones	Easy	array
487	Max Consecutive Ones II	Medium	array
495	Teemo Attacking	Easy	array
498	Diagonal Traverse	Medium	array
506	Relative Ranks	Easy	array
531	Lonely Pixel I	Medium	array
533	Lonely Pixel II	Medium	array
565	Array Nesting	Medium	array
566	Reshape the Matrix	Easy	array
581	Shortest Unsorted Continuous Subarray	Easy	array
605	Can Place Flowers	Easy	array
624	Maximum Distance in Arrays	Easy	array
643	Maximum Average Subarray I	Easy	array
644	Maximum Average Subarray II	Hard	array
661	Image Smoother	Easy	array
665	Non-decreasing Array	Easy	array
667	Beautiful Arrangement II	Medium	array
670	Maximum Swap	Medium	array
674	Longest Continuous Increasing Subsequence	Easy	array
683	K Empty Slots	Hard	array
697	Degree of an Array	Easy	array
713	Subarray Product Less Than K	Medium	array
717	1-bit and 2-bit Characters	Easy	array
723	Candy Crush	Medium	array
724	Find Pivot Index	Easy	array
729	My Calendar I	Medium	array
731	My Calendar II	Medium	array
732	My Calendar III	Hard	array
747	Largest Number At Least Twice of Others	Easy	array
755	Pour Water	Medium	array
766	Toeplitz Matrix	Easy	array
768	Max Chunks To Make Sorted II	Hard	array
769	Max Chunks To Make Sorted	Medium	array
778	Swim in Rising Water	Hard	array
792	Number of Matching Subsequences	Medium	array
794	Valid Tic-Tac-Toe State	Medium	array
795	Number of Subarrays with Bounded Maximum	Medium	array
803	Bricks Falling When Hit	Hard	array
807	Max Increase to Keep City Skyline	Medium	array
821	Shortest Distance to a Character	Easy	array
830	Positions of Large Groups	Easy	array
832	Flipping an Image	Easy	array
835	Image Overlap	Medium	array
840	Magic Squares In Grid	Easy	array
842	Split Array into Fibonacci Sequence	Medium	array
845	Longest Mountain in Array	Medium	array
849	Maximize Distance to Closest Person	Easy	array
860	Lemonade Change	Easy	array
867	Transpose Matrix	Easy	array
885	Spiral Matrix III	Medium	array
888	Fair Candy Swap	Easy	array
896	Monotonic Array	Easy	array
905	Sort Array By Parity	Easy	array
909	Snakes and Ladders	Medium	array
915	Partition Array into Disjoint Intervals	Medium	array
918	Maximum Sum Circular Subarray	Medium	array
922	Sort Array By Parity II	Easy	array
923	3Sum With Multiplicity	Medium	array
927	Three Equal Parts	Hard	array
932	Beautiful Array	Medium	array
941	Valid Mountain Array	Easy	array
945	Minimum Increment to Make Array Unique	Medium	array
947	Most Stones Removed with Same Row or Column	Medium	array
949	Largest Time for Given Digits	Easy	array
950	Reveal Cards In Increasing Order	Medium	array
952	Largest Component Size by Common Factor	Hard	array
954	Array of Doubled Pairs	Medium	array
961	N-Repeated Element in Size 2N Array	Easy	array
978	Longest Turbulent Subarray	Medium	array
985	Sum of Even Numbers After Queries	Easy	array
989	Add to Array-Form of Integer	Easy	array
997	Find the Town Judge	Easy	array
999	Available Captures for Rook	Easy	array
1002	Find Common Characters	Easy	array
1007	Minimum Domino Rotations For Equal Row	Medium	array
1010	Pairs of Songs With Total Durations Divisible by 60	Easy	array
1013	Partition Array Into Three Parts With Equal Sum	Easy	array
1014	Best Sightseeing Pair	Medium	array
1018	Binary Prefix Divisible By 5	Easy	array
1030	Matrix Cells in Distance Order	Easy	array
1031	Maximum Sum of Two Non-Overlapping Subarrays	Medium	array
1051	Height Checker	Easy	array
1052	Grumpy Bookstore Owner	Medium	array
1072	Flip Columns For Maximum Number of Equal Rows	Medium	array
1074	Number of Submatrices That Sum to Target	Hard	array
1085	Sum of Digits in the Minimum Number	Easy	array
1089	Duplicate Zeros	Easy	array
1093	Statistics from a Large Sample	Medium	array
1099	Two Sum Less Than K	Easy	array
1109	Corporate Flight Bookings	Medium	array
1144	Decrease Elements To Make Array Zigzag	Medium	array
1184	Distance Between Bus Stops	Easy	array
1200	Minimum Absolute Difference	Easy	array
1222	Queens That Can Attack the King	Medium	array
1252	Cells with Odd Values in a Matrix	Easy	array
1260	Shift 2D Grid	Easy	array
1267	Count Servers that Communicate	Medium	array
1275	Find Winner on a Tic Tac Toe Game	Easy	array
1295	Find Numbers with Even Number of Digits	Easy	array
1299	Replace Elements with Greatest Element on Right Side	Easy	array
1304	Find N Unique Integers Sum up to Zero	Easy	array
1313	Decompress Run-Length Encoded List	Easy	array
1329	Sort the Matrix Diagonally	Medium	array
1331	Rank Transform of an Array	Easy	array
1333	Filter Restaurants by Vegan-Friendly, Price and Distance	Medium	array
1337	The K Weakest Rows in a Matrix	Easy	array
1343	Number of Sub-arrays of Size K and Average Greater than or Equal to Threshold	Medium	array
1346	Check If N and Its Double Exist	Easy	array
1351	Count Negative Numbers in a Sorted Matrix	Easy	array
1375	Bulb Switcher III	Medium	array
1380	Lucky Numbers in a Matrix	Easy	array
1389	Create Target Array in the Given Order	Easy	array
1394	Find Lucky Integer in an Array	Easy	array
1399	Count Largest Group	Easy	array
1404	Number of Steps to Reduce a Number in Binary Representation to One	Medium	array
1413	Minimum Value to Get Positive Step by Step Sum	Easy	array
1426	Counting Elements	Easy	array
1427	Perform String Shifts	Easy	array
1428	Leftmost Column with at Least a One	Medium	array
1431	Kids With the Greatest Number of Candies	Easy	array
1437	Check If All 1's Are at Least Length K Places Away	Medium	array
1450	Number of Students Doing Homework at a Given Time	Easy	array
1460	Make Two Arrays Equal by Reversing Sub-arrays	Easy	array
1464	Maximum Product of Two Elements in an Array	Easy	array
1465	Maximum Area of a Piece of Cake After Horizontal and Vertical Cuts	Medium	array
1470	Shuffle the Array	Easy	array
1471	The k Strongest Values in an Array	Medium	array
1475	Final Prices With a Special Discount in a Shop	Easy	array
1480	Running Sum of 1d Array	Easy	array
1491	Average Salary Excluding the Minimum and Maximum Salary	Easy	array
1502	Can Make Arithmetic Progression From Sequence	Easy	array
1503	Last Moment Before All Ants Fall Out of a Plank	Medium	array
1534	Count Good Triplets	Easy	array
1535	Find the Winner of an Array Game	Medium	array
1538	Guess the Majority in a Hidden Array	Medium	array
1550	Three Consecutive Odds	Easy	array
1559	Detect Cycles in 2D Grid	Hard	array
1560	Most Visited Sector in a Circular Track	Easy	array
1562	Find Latest Group of Size M	Medium	array
1566	Detect Pattern of Length M Repeated K or More Times	Easy	array
1572	Matrix Diagonal Sum	Easy	array
1574	Shortest Subarray to be Removed to Make Array Sorted	Medium	array
1582	Special Positions in a Binary Matrix	Easy	array
1583	Count Unhappy Friends	Medium	array
1619	Mean of Array After Removing Some Elements	Easy	array
1629	Slowest Key	Easy	array
1646	Get Maximum in Generated Array	Easy	array
1652	Defuse the Bomb	Easy	array
1672	Richest Customer Wealth	Easy	array
1700	Number of Students Unable to Eat Lunch	Easy	array
1701	Average Waiting Time	Medium	array
1706	Where Will the Ball Fall	Medium	array
1714	Sum Of Special Evenly-Spaced Elements In Array	Hard	array
1726	Tuple with Same Product	Medium	array
1732	Find the Highest Altitude	Medium	array
1738	Find Kth Largest XOR Coordinate Value	Medium	array
1742	Maximum Number of Balls in a Box	Easy	array
1752	Check if Array Is Sorted and Rotated	Easy	array
1755	Closest Subsequence Sum	Hard	array
1773	Count Items Matching a Rule	Easy	array
1779	Find Nearest Point That Has the Same X or Y Coordinate	Easy	array
1800	Maximum Ascending Subarray Sum	Easy	array
1826	Faulty Sensor	Easy	array
1848	Minimum Distance to the Target Element	Easy	array
1861	Rotating the Box	Medium	array
1869	Longer Contiguous Segments of Ones than Zeros	Easy	array
1878	Get Biggest Three Rhombus Sums in a Grid	Easy	array
1886	Determine Whether Matrix Can Be Obtained By Rotation	Easy	array
1895	Largest Magic Square	Medium	array
1906	Minimum Absolute Difference Queries	Medium	array
1909	Remove One Element to Make the Array Strictly Increasing	Easy	array
1914	Cyclically Rotating a Grid	Medium	array
1920	Build Array from Permutation	Easy	array
1929	Concatenation of Array	Easy	array
1940	Longest Common Subsequence Between Sorted Arrays	Medium	array
1958	Check if Move is Legal	Medium	array
1966	Binary Searchable Numbers in an Unsorted Array	Medium	array
1970	Last Day Where You Can Still Cross	Hard	array
1983	Widest Pair of Indices With Equal Range Sum	Medium	array
1991	Find the Middle Index in Array	Easy	array
1992	Find All Groups of Farmland	Medium	array
1998	GCD Sort of an Array	Hard	array
2007	Find Original Array From Doubled Array	Medium	array
2011	Final Value of Variable After Performing Operations	Easy	array
2012	Sum of Beauty in the Array	Medium	array
2016	Maximum Difference Between Increasing Elements	Easy	array
2017	Grid Game	Medium	array
2018	Check if Word Can Be Placed In Crossword	Medium	array
2022	Convert 1D Array Into 2D Array	Easy	array
2033	Minimum Operations to Make a Uni-Value Grid	Medium	array
2035	Partition Array Into Two Arrays to Minimize Sum Difference	Hard	array
2038	Remove Colored Pieces if Both Neighbors are the Same Color	Medium	array
2055	Plates Between Candles	Medium	array
2057	Smallest Index With Equal Value	Easy	array
2075	Decode the Slanted Ciphertext	Medium	array
2078	Two Furthest Houses With Different Colors	Easy	array
2079	Watering Plants	Medium	array
2098	Subsequence of Size K With the Largest Even Sum	Medium	array
2099	Find Subsequence of Length K With the Largest Sum	Easy	array
2100	Find Good Days to Rob the Bank	Medium	array
2106	Maximum Fruits Harvested After at Most K Steps	Hard	array
2113	Elements in Array After Removing and Replacing Elements	Medium	array
2121	Intervals Between Identical Elements	Medium	array
2122	Recover the Original Array	Hard	array
2128	Remove All Ones With Row and Column Flips	Medium	array
2132	Stamping the Grid	Hard	array
2155	All Divisions With the Highest Score of a Binary Array	Medium	array
2194	Cells in a Range on an Excel Sheet	Easy	array
2210	Count Hills and Valleys in an Array	Easy	array
2219	Maximum Sum Score of Array	Medium	array
2237	Count Positions on Street With Required Brightness	Medium	array
2239	Find Closest Number to Zero	Easy	array
2245	Maximum Trailing Zeros in a Cornered Path	Medium	array
2256	Minimum Average Difference	Medium	array
2270	Number of Ways to Split Array	Medium	array
2271	Maximum White Tiles Covered by a Carpet	Medium	array
2274	Maximum Consecutive Floors Without Special Floors	Medium	array
2293	Min Max Game	Medium	array
2319	Check if Matrix Is X-Matrix	Easy	array
2326	Spiral Matrix IV	Medium	array
2373	Largest Local Values in a Matrix	Easy	array
2382	Maximum Segment Sum After Removals	Hard	array
2391	Minimum Amount of Time to Collect Garbage	Medium	array
2406	Divide Intervals Into Minimum Number of Groups	Medium	array
2407	Longest Increasing Subsequence II	Hard	array
2428	Maximum Sum of an Hourglass	Medium	array
2432	The Employee That Worked on the Longest Task	Easy	array
2433	Find The Original Array of Prefix Xor	Medium	array
2438	Range Product Queries of Powers	Medium	array
2446	Determine if Two Events Have Conflict	Easy	array
2460	Apply Operations to an Array	Easy	array
2482	Difference Between Ones and Zeros in Row and Column	Medium	array
2500	Delete Greatest Value in Each Row	Easy	array
2515	Shortest Distance to Target String in a Circular Array	Easy	array
2535	Difference Between Element Sum and Digit Sum of an Array	Easy	array
2536	Increment Submatrices by One	Medium	array
2553	Separate the Digits in an Array	Easy	array
2559	Count Vowel Strings in Ranges	Medium	array
2569	Handling Sum Queries After Update	Hard	array
2574	Left and Right Sum Differences	Easy	array
2580	Count Ways to Group Overlapping Ranges	Medium	array
2639	Find the Width of Columns of a Grid	Easy	array
2640	Find the Score of All Prefixes of an Array	Medium	array
2643	Row With Maximum Ones	Easy	array
2644	Find the Maximum Divisibility Score	Easy	array
2655	Find Maximal Uncovered Ranges	Medium	array
2660	Determine the Winner of a Bowling Game	Medium	array
2672	Number of Adjacent Elements With the Same Color	Medium	array
2683	Neighboring Bitwise XOR	Medium	array
2711	Difference of Number of Distinct Values on Diagonals	Medium	array
2717	Semi-Ordered Permutation	Easy	array
2733	Neither Minimum nor Maximum	Easy	array
2760	Longest Even Odd Subarray With Threshold	Easy	array
2765	Longest Alternating Subarray	Easy	array
2782	Number of Unique Categories	Medium	array
2798	Number of Employees Who Met the Target	Easy	array
2848	Points That Intersect With Cars	Easy	array
2855	Minimum Right Shifts to Sort the Array	Easy	array
2873	Maximum Value of an Ordered Triplet I	Easy	array
2874	Maximum Value of an Ordered Triplet II	Easy	array
2903	Find Indices With Index and Value Difference I	Easy	array
2905	Find Indices With Index and Value Difference II	Medium	array
2906	Construct Product Matrix	Medium	array
2908	Minimum Sum of Mountain Triplets I	Easy	array
2909	Minimum Sum of Mountain Triplets II	Medium	array
2923	Find Champion I	Easy	array
2946	Matrix Similarity After Cyclic Shifts	Easy	array
2951	Find the Peaks	Easy	array
2965	Find Missing and Repeated Values	Easy	array
2966	Divide Array Into Arrays With Max Difference	Medium	array
3000	Maximum Area of Longest Diagonal Rectangle	Easy	array
3009	Maximum Number of Intersections on the Chart	Hard	array
3010	Divide an Array Into Subarrays With Minimum Cost I	Easy	array
3015	Count the Number of Houses at a Certain Distance I	Medium	array
3017	Count the Number of Houses at a Certain Distance II	Hard	array
3026	Maximum Good Subarray Sum	Medium	array
3028	Ant on the Boundary	Easy	array
3030	Find the Grid of Region Average	Medium	array
3033	Modify the Matrix	Easy	array
3038	Maximum Number of Operations With the Same Score I	Easy	array
3065	Minimum Operations to Exceed Threshold Value I	Easy	array
3069	Distribute Elements Into Two Arrays I	Easy	array
3070	Count Submatrices with Top-Left Element and Sum Less Than k	Medium	array
3071	Minimum Operations to Write the Letter Y on a Grid	Medium	array
3079	Find the Sum of Encrypted Integers	Easy	array
3096	Minimum Levels to Gain More Points	Medium	array
3105	Longest Strictly Increasing or Strictly Decreasing Subarray	Easy	array
3127	Make a Square with the Same Color	Easy	array
3131	Find the Integer Added to Array I	Easy	array
3142	Check if Grid Satisfies Conditions	Easy	array
3147	Taking Maximum Energy From the Mystic Dungeon	Medium	array
3151	Special Array I	Easy	array
3152	Special Array II	Medium	array
3153	Sum of Digit Differences of All Pairs	Medium	array
3159	Find Occurrences of an Element in an Array	Medium	array
3173	Bitwise OR of Adjacent Elements	Easy	array
3187	Peaks in Array	Hard	array
3195	Find the Minimum Area to Cover All Ones I	Medium	array
3224	Minimum Array Changes to Make Differences Equal	Medium	array
3279	Maximum Total Area Occupied by Pistons	Hard	array
3285	Find Indices of Stable Mountains	Easy	array
3300	Minimum Element After Replacement With Digit Sum	Easy	array
3330	Find the Original Typed String I	Easy	array
3334	Find the Maximum Factor Score of Array	Medium	array
3349	Adjacent Increasing Subarrays Detection I	Easy	array
3350	Adjacent Increasing Subarrays Detection II	Medium	array
3353	Minimum Total Operations	Easy	array
3354	Make Array Elements Equal to Zero	Easy	array
3355	Zero Array Transformation I	Medium	array
3361	Shift Distance Between Two Strings	Medium	array
3379	Transformed Array	Easy	array
3380	Maximum Area Rectangle With Point Constraints I	Medium	array
3382	Maximum Area Rectangle With Point Constraints II	Hard	array
3386	Button with Longest Push Time	Easy	array
3392	Count Subarrays of Length Three With a Condition	Easy	array
3400	Maximum Number of Matching Indices After Right Shifts	Medium	array
3417	Zigzag Grid Traversal With Skip	Easy	array
3423	Maximum Difference Between Adjacent Elements in a Circular Array	Easy	array
3427	Sum of Variable Length Subarrays	Easy	array
3432	Count Partitions with Even Sum Difference	Easy	array
3440	Reschedule Meetings for Maximum Free Time II	Medium	array
3446	Sort Matrix by Diagonals	Medium	array
3452	Sum of Good Numbers	Easy	array
3467	Transform Array by Parity	Easy	array
3502	Minimum Cost to Reach Every Position	Easy	array
3514	Number of Unique XOR Triplets II	Medium	array
3531	Count Covered Buildings	Medium	array
3537	Fill a Special Grid	Medium	array
3540	Minimum Time to Visit All Houses	Medium	array
3546	Equal Sum Grid Partition I	Medium	array
3548	Equal Sum Grid Partition II	Hard	array
3549	Multiply Two Polynomials	Hard	array
3550	Smallest Index With Digit Sum Equal to Index	Easy	array
3569	Maximize Count of Distinct Primes After Split	Medium	array
3637	Trionic Array I	Easy	array
3643	Flip Square Submatrix Vertically	Easy	array
3653	XOR After Range Multiplication Queries I	Medium	array
3655	XOR After Range Multiplication Queries II	Hard	array
3674	Minimum Operations to Equalize Array	Easy	array
3683	Earliest Time to Finish One Task	Easy	array
3687	Library Late Fee Calculator	Easy	array
3688	Bitwise OR of Even Numbers in an Array	Easy	array
3696	Maximum Distance Between Unequal Words in Array I	Easy	array
3700	Number of ZigZag Arrays II	Hard	array
3701	Compute Alternating Sum	Easy	array
3706	Maximum Distance Between Unequal Words in Array II	Medium	array
3707	Equal Score Substrings	Easy	array
3708	Longest Fibonacci Subarray	Medium	array
3719	Longest Balanced Subarray I	Medium	array
3721	Longest Balanced Subarray II	Hard	array
3736	Minimum Moves to Equal Array Elements III	Easy	array
3737	Count Subarrays With Majority Element I	Medium	array
3738	Longest Non-Decreasing Subarray After Replacing at Most One Element	Medium	array
3739	Count Subarrays With Majority Element II	Hard	array
3751	Total Waviness of Numbers in Range I	Medium	array
3756	Concatenate Non-Zero Digits and Multiply by Sum II	Medium	array
3762	Minimum Operations to Equalize Subarrays	Hard	array
3774	Absolute Difference Between Maximum and Minimum K Elements	Easy	array
3788	Maximum Score of a Split	Medium	array
3809	Best Reachable Tower	Medium	array
3814	Maximum Capacity Within Budget	Medium	array
3818	Minimum Prefix Removal to Make Array Strictly Increasing	Medium	array
3819	Rotate Non Negative Elements	Medium	array
3833	Count Dominant Indices	Easy	array
3861	Minimum Capacity Box	Easy	array
3862	Find the Smallest Balanced Index	Medium	array
3865	Reverse K Subarrays	Medium	array
3880	Minimum Absolute Difference Between Two Values	Easy	array
3886	Sum of Sortable Integers	Hard	array
3898	Find the Degree of Each Vertex	Easy	array
3903	Smallest Stable Index I	Easy	array
3904	Smallest Stable Index II	Medium	array
3907	Count Smaller Elements With Opposite Parity	Medium	array
3909	Compare Sums of Bitonic Parts	Medium	array
3912	Valid Elements in an Array	Medium	array
3918	Sum of Primes Between Number and Its Reverse	Medium	array
3925	Concatenate Array With Reverse	Easy	array
3933	Largest Local Values in a Matrix II	Medium	array
3936	Minimum Swaps to Move Zeros to End	Easy	array
3938	Maximum Path Intersection Sum in a Grid	Medium	array
3940	Limit Occurrences in Sorted Array	Easy	array
3942	Minimum Operations to Sort a Permutation	Medium	array
3943	Number of Pairs After Increment	Hard	array
3951	Minimum Energy to Maintain Brightness	Medium	array
3963	Create Grid With Exactly One Path	Easy	array
3978	Unique Middle Element	Easy	array
3979	Maximum Valid Pair Sum	Medium	array
3982	Sum of Integers with Maximum Digit Range	Easy	array
3985	Palindromic Subarray Sum	Hard	array