Data Structures Notes

Meeting Rooms (Can Attend All Meetings)

Meeting Rooms (LeetCode 252): sort meetings by start and check that none overlaps the previous one. O(n log n), Python/Java/C++.

Data Structures

H-Index (Sorting Approach)

H-Index (LeetCode 274) via sorting: sort citations descending and find the largest i where citations[i] >= i+1. O(n log n), Python/Java/C++.

Data Structures

Wiggle Sort II

Wiggle Sort II (LeetCode 324): strict nums[0] < nums[1] > nums[2]... via sorting and interleaving the two halves in reverse. O(n log n), Python/Java/C...

Data Structures

Wiggle Sort

Wiggle Sort (LeetCode 280): rearrange so nums[0] = nums[2]

Data Structures

Relative Sort Array

Relative Sort Array (LeetCode 1122): sort by the order defined in a second array, with the rest sorted ascending. O(n log n), Python/Java/C++.

Data Structures

Kth Largest Element (Sorting Approach)

Kth Largest Element (LeetCode 215) via sorting: sort and index from the end in O(n log n), with a note on the O(n)-average quickselect alternative.

Data Structures

Sort Characters By Frequency

Sort Characters By Frequency (LeetCode 451): count characters, then sort by descending frequency and rebuild the string. O(n + k log k), Python/Java/C...

Data Structures

Custom Sort String

Custom Sort String (LeetCode 791): sort one string by the character priority defined in another, using a rank map. O(n log n) or O(n), Python/Java/C++...

Data Structures

Largest Number Formed from an Array

Largest Number (LeetCode 179): sort numbers by a custom pairwise rule (a+b vs b+a) to form the biggest concatenation. O(n log n), Python/Java/C++.

Data Structures

Merge Intervals Using Sorting

Merge Intervals (LeetCode 56): sort by start, then merge overlapping intervals in one pass. O(n log n), with Python, Java and C++ code.

Data Structures

Sort an Array (Built-in vs Custom Comparator)

Sort an Array (LeetCode 912): how to use built-in sorts and custom comparators in Python, Java and C++, including ascending, descending and key-based...

Data Structures

Bucket Sort Implementation

Bucket sort explained: scatter elements into buckets by range, sort each bucket, then concatenate. O(n) average for uniform data, in Python, Java and...