A2Z DSA Sheet

Input and output, data types, if-else, switch, loops and functions, plus how to reason about time complexity.

Working with digits, palindromic and Armstrong numbers, GCD, divisors and primality.

Build intuition for recursion on small problems: printing ranges, sums, factorials, reversing and palindrome checks.

Frequency counting with arrays and hash maps, and finding the most and least frequent elements.

The classic sorts (selection, bubble, insertion, merge and quick), including their recursive versions.

From single-pass scans to Kadane's algorithm, the k-Sum family, matrix problems, intervals and inversion counting.

Bounds on sorted arrays, rotated arrays, searching over the answer space (Koko, Aggressive Cows, Book Allocation) and 2D matrices.

Everyday string problems: parentheses, anagrams, isomorphism, Roman numerals, atoi and substring counting.

Singly and doubly linked lists end to end: insert, delete, reverse, detect cycles, sort and deep-copy.

Generate subsequences and combinations, then backtrack through N-Queens, Sudoku, mazes and graph colouring.

Bitwise operators in practice: test and set bits, count set bits, XOR tricks and subset generation.

Stack and queue implementations, expression conversion, monotonic stacks, and LRU and LFU cache design.

Window and pointer techniques for the longest and shortest substring and subarray problems.

Priority-queue problems: k-th order statistics, merging sorted data, scheduling and running medians.

Locally optimal choices that add up: knapsack variants, jump games, job sequencing and interval scheduling.

Recursive, iterative and Morris traversals, tree views, diameter and width, LCA, construction and serialization.

BST operations and properties: search, insert, delete, floor and ceil, validation, successors and recovery.

Traversals, cycle detection, topological ordering, shortest paths, MSTs, union-find and strongly connected components.

A complete DP progression: 1D, grids, subsets, strings, stocks, LIS and partition DP.

Prefix trees for word and prefix queries, and bitwise tries for maximum-XOR problems.

String matching algorithms (hashing, Rabin-Karp, Z-function and KMP) and the problems they unlock.