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Algorithms and Data Structures

12 chapters

01Complexity and Problem-Solving Thinking

Big-O and Trade-offs

time complexity, space complexity, amortized analysis, trade-off thinking

Beginner→

Problem Decomposition

constraints, input modeling, edge cases, invariants

Beginner→

From Brute Force to Optimization

baseline solution, optimization path, pattern selection, complexity improvement

Intermediate→

02Arrays and Strings

Array Basics

index access, in-place updates, iteration patterns, edge cases

Beginner→

Strings and Character Frequency

frequency counting, two-pass scans, anagram patterns, normalization

Beginner→

Prefix Sum and Difference Thinking

prefix sum, range queries, subarray sums, difference arrays

Intermediate→

03Linked Lists, Stacks, and Queues

Linked Lists

pointer updates, dummy nodes, reversal, cycle detection

Intermediate→

Stacks and Monotonic Stacks

LIFO, balanced parentheses, next greater element, monotonic patterns

Intermediate→

Queues, Deques, and BFS Foundations

FIFO, deque usage, level-order traversal, state expansion

Intermediate→

04HashMaps, Sets, and Counting Patterns

HashMap Basics

lookup, insert, complements, deduplication

Beginner→

Frequency and Counting Patterns

frequency maps, buckets, grouping, majority patterns

Intermediate→

Hash Trade-offs and Edge Cases

collisions, ordering, memory trade-offs, pathological cases

Intermediate→

05Two Pointers, Sliding Window, and Intervals

Two Pointers

sorted arrays, convergence, partitioning, pair matching

Intermediate→

Sliding Window

variable window, fixed window, frequency constraints, window invariants

Intermediate→

Interval Problems

merge intervals, meeting rooms, line sweep basics, overlap logic

Intermediate→

06Binary Search, Sorting, and Selection

Binary Search Patterns

mid calculation, lower bound, upper bound, search on answer

Intermediate→

Sorting Strategies

comparison sort, stable sorting, custom comparators, sort then scan

Intermediate→

Heaps and Top-K

priority queue, k largest, streaming top-k, heap trade-offs

Intermediate→

07Trees, Heaps, and Tries

Binary Trees and Traversals

DFS, BFS, recursive traversal, iterative traversal

Intermediate→

BST and Balanced Thinking

BST invariants, ordered traversal, height, pruning

Intermediate→

Heaps and Tries

min heap, max heap, prefix trees, autocomplete patterns

Advanced→

08Graphs, BFS, DFS, and Union-Find

Graph Representation

adjacency list, adjacency matrix, directed graphs, weighted graphs

Intermediate→

BFS and DFS Patterns

connected components, shortest path in unweighted graphs, flood fill, back edge detection

Advanced→

Union-Find and Topological Sort

disjoint set union, path compression, cycle detection, DAG ordering

Advanced→

09Recursion, Backtracking, and Divide and Conquer

Recursion Thinking

base case, call stack, state contraction, recursive invariants

Intermediate→

Backtracking Patterns

choices, constraints, pruning, permutations and combinations

Advanced→

Divide and Conquer

merge sort reasoning, quickselect, problem splitting, combine phase

Advanced→

10Dynamic Programming and Greedy

Greedy Thinking

local optimum, exchange argument, interval scheduling, MST intuition

Intermediate→

DP Basics

state, transition, memoization, tabulation

Advanced→

Classic DP Patterns

knapsack, LCS, grid DP, subsequence DP

Advanced→

11Bit Manipulation, Math, and String Algorithms

Bit Manipulation

bit masks, xor tricks, set bits, power-of-two patterns

Intermediate→

Math Algorithms

gcd, sieve, modular arithmetic, combinatorics basics

Intermediate→

String Matching

substring search, KMP, Rabin-Karp, rolling hash basics

Advanced→

12LeetCode Patterns and Interview Strategy

Pattern Recognition

problem signals, pattern mapping, input clues, constraint-based selection

Intermediate→

Explaining Solutions Clearly

communicating trade-offs, stating invariants, complexity explanation, interview narration

Intermediate→

Common Mistakes and Recovery

off-by-one, missed edge cases, incorrect state updates, self-correction strategy

Advanced→