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Arrays

From scans and prefix sums to Kadane and in-place rewrites.

7 stops · 250 problems0/101 on the path done
next ▸ Running Sum of a 1D ArraySilver · 1000
1

Scans & aggregates

0/16 of 22you are here

Single-pass sums, running totals, min/max.

○Running Sum of a 1D Array○Running Sum of 1d Array○Concatenation of Array○Final Value After Operations○Maximum Ascending Subarray Sum○Sum of Unique Elements○Find the Highest Altitude○Kids With the Greatest Number of Candies○Build Array from Permutation○Running Sum Of Array○Richest Customer Wealth○Number of Good Pairs○Kids With the Greatest Candies○Count Good Pairs○Decompress Run-Length Encoded List○Final Value of Variable After Operations+6 in the arena
2

Prefix & product

0/15

Prefix sums, product-except-self, range tricks.

○Sum of Absolute Differences○Running Prefix Sum○Find Pivot Index○Count Pairs With Absolute Difference K○Range Sum Query (Offline)○Maximum Difference Between Increasing Elements○Max Difference○Count Number of Pairs With Absolute Difference K○Left And Right Sum Difference○Find the Difference of Two Arrays○Find the Distinct Difference Array○Contiguous Array Equal Zeros and Ones○Minimum Value to Get Positive Step by Step Sum○Subarray Sums Divisible by 7○Product Except Self
3

Kadane & subarrays

0/16 of 28

Maximum subarray, circular variants, windows.

○Longest Subarray Sum At Most K○Longest Subarray of 1's After Deleting One○Shortest Unsorted Continuous Subarray○Longest Turbulent Subarray○Sum of All Odd Length Subarrays○Maximum Average Subarray○Degree of an Array○Maximum Erasure Value○Max Sum of Two Non-Overlapping Subarrays○Max Consecutive Ones III○Number of Arithmetic Subarrays○Longest Subarray of Ones After One Deletion○Longest Subarray With Two Distinct○Maximum Subarray Sum○Subarray Product Less Than K○Maximum Sum Circular Subarray+12 in the arena
4

Two-pass & in-place

0/13

Rewrite arrays in place; rotate, move, sort colors.

○Rotate Array Right by K○Sort Colors (Dutch Flag)○Rotate Array Left by K○Remove Duplicates from Sorted Array○Move Zeroes○Rotate Array○Find Minimum in Rotated Sorted Array○Move Zeroes to End○Remove Duplicates Allow Twice○Rotate By One○Merge Sorted Arrays In Place○Merge Sorted Array In Place○Next Permutation
5

Counting & lookups

0/16 of 17

Duplicates, majority, single number, intersections.

○Find All Numbers Disappeared○Set Mismatch○Kth Missing Positive Number○Intersection of Multiple Arrays○Third Maximum Number○Find the Missing Number○Find the Duplicate and Missing Pair○Intersection Of Two Sorted Arrays○Find Disappeared Numbers○Third Maximum○Majority Elements Over n/3○Find All Disappeared Numbers○Common Elements Sorted○Find Disappeared Numbers (Sorted)○First Missing Positive○Find Missing Observations+1 in the arena
6

Search & two pointers

0/9

Rotated search, peaks, 3-sum, water.

○Two Sum (Sorted, 1-Indexed)○Two Sum Indices○Count Mountain Peaks○Two Sum Less Than K○Find Peak Element Index○Find a Peak Element○Three Sum Unique Triplets○Find a Peak Index○Three Sum Triplet Count
7

More Arrays

0/16 of 146

Everything else in this category — keep climbing.

○Sum of an Array○Count Elements Equal to Maximum○Count Zeros○Min and Max○Reverse an Array○Find Lucky Integer○Count Elements With Smaller and Greater○Maximum Product of Two Elements Minus One○Three Consecutive Odds○Shuffle the Array○Count Even And Odd○Sum Of Positives○Remove Element In Place○Can Place Flowers○Minimum Operations to Make Array Equal○Can Make Arithmetic Progression+130 in the arena
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