Data Structures
Find Right Interval
Find Right Interval (LeetCode 436): sort interval starts and binary-search the smallest start >= each interval end, O(n log n).
Data Structures
Arrays, Strings, Sliding Window, Two Pointers, Searching & Binary Search, Sorting, Linked List, Stack & Queue, Recursion & Backtracking, Trees, Heap / Priority Queue, Graphs, Dynamic Programming, Greedy, Bit Manipulation, Trie, Math & Number Theory, Design (LLD / OOP), SQL, System Design (HLD)
180 notes in 20 topics
Topics in Data Structures
Arrays 30
Strings 35
Sliding Window 35
Two Pointers 30
Searching & Binary Search 30
Sorting 25
Linked List 0
Stack & Queue 0
Recursion & Backtracking 0
Trees 0
Heap / Priority Queue 0
Graphs 0
Dynamic Programming 0
Greedy 0
Bit Manipulation 0
Trie 0
Math & Number Theory 0
Design (LLD / OOP) 0
SQL 0
System Design (HLD) 0
Notes
Data Structures
Random Pick with Weight
Random Pick with Weight (LeetCode 528): build prefix sums and binary-search a random target for O(log n) weighted sampling.
Data Structures
Interview Concept: Lower Bound vs Upper Bound Binary Search
Lower bound vs upper bound binary search explained: first index >= target vs first index > target, with ready templates in Python, Java and C++.
Data Structures
Interview Concept: Binary Search on Answer Pattern Explained
The "binary search on the answer" pattern explained: when the answer space has a monotone yes/no predicate, binary-search the answer itself. With a re...
Data Structures
Bubble Sort Implementation
Bubble sort explained simply: repeatedly swap adjacent out-of-order items, with an early-exit optimisation. O(n^2) time, stable, in Python, Java and C...
Data Structures
Selection Sort Implementation
Selection sort explained: repeatedly pick the smallest remaining element and place it next. O(n^2) time with the fewest swaps, in Python, Java and C++...
Data Structures
Insertion Sort Implementation
Insertion sort explained: build a sorted prefix by inserting each element into place. O(n^2) worst but O(n) on nearly sorted data; stable, in Python...
Data Structures
Merge Sort Implementation
Merge sort explained: divide the array in half, sort each half, then merge. Guaranteed O(n log n), stable, with Python, Java and C++ code.
Data Structures
Quick Sort Implementation
Quick sort explained: partition around a pivot and recurse. O(n log n) average, in-place, with the Lomuto partition in Python, Java and C++.
Data Structures
Heap Sort Implementation
Heap sort explained: build a max-heap, then repeatedly move the max to the end. O(n log n) worst case, in-place, with Python, Java and C++ code.
Data Structures
Counting Sort Implementation
Counting sort explained: tally occurrences of each value, then rebuild the array. O(n + k) time for small integer ranges, in Python, Java and C++.
Data Structures
Radix Sort Implementation
Radix sort explained: sort integers digit by digit using a stable counting sort per digit. O(d(n + k)) time, in Python, Java and C++.