🎯 Google-Ready 100 — শূন্য থেকে interview + job-ready পথ

এই repo-র 446 problem থেকে বেছে নেওয়া ঠিক ১০০টা — যাতে একদম শূন্য থেকে শুরু করা একজন learner ধাপে ধাপে এমন জায়গায় পৌঁছায় যেখান থেকে Google/FAANG interview দেওয়া যায়, আর একই সাথে real job-এ কাজ করার মতো pattern হাতে আসে।

নীতি: প্রতিটা গুরুত্বপূর্ণ pattern একবার করে, তার সবচেয়ে canonical problem দিয়ে। duplicate নেই, fluff নেই — শুধু যেগুলো বারবার interview-তে আর production-এ ফিরে আসে।

কীভাবে ব্যবহার করবে

• ক্রম ধরে এগোও (Stage 1 → 14)। প্রতিটা stage আগেরটার উপর দাঁড়ায়।
• প্রতিটা problem-এর full Bangla note + Python + JavaScript + TypeScript solution + test cases + real-world use ওই problem-এর .md file-এ (link দেওয়া আছে)।
• প্রতিদিন 2–4টা; একটা problem মানে শুধু solve নয় — pattern-টা মুখে বলে বোঝা।
• কোনোটায় আটকালে brute force → optimize ধাপটা note-এ আছে, ওটা পড়ো।

Difficulty: 🟢 Easy · 🟡 Medium · 🔴 Hard Status: ✅ = নোটে JS/TS, test ও use-case অংশ আছে। এটি আপনার solve status বা সব solution যাচাইয়ের সনদ নয়। নিজের অগ্রগতি আলাদা রাখুন।

Problem নামের link থেকে বাংলা নোট খুলুন; নোটের source অংশে official judge link পাবেন। নিজস্ব exercise হলে সেটি সেখানে লেখা আছে।

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Stage 1 — Math ও Number Foundations (8)

%, digit loop, prime, gcd/lcm, modular power — সব pattern-এর শিকড়।

#	Problem	Diff	Pattern / Skill	কেন জরুরি	Status
1	Even or Odd	🟢	parity, %, bit	প্রথম pattern; sharding/parity bit	✅
2	Sum of Digits	🟢	digit extraction loop	checksum/Luhn-এর ভিত্তি	✅
3	Count Digits	🟢	digit loop, log10	validation/padding	✅
4	Check Prime	🟢	trial division √n	crypto/number theory গেট	✅
5	Sieve of Eratosthenes	🟡	sieve precompute	bulk prime, precomputation mindset	✅
6	GCD (Euclidean)	🟢	Euclid recursion	fractions, scheduling	✅
7	LCM using GCD	🟢	gcd→lcm relation	cycles, overflow-safe math	✅
8	Modular Exponentiation	🟡	fast power O(log n)	crypto, hashing, big powers	✅

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Stage 2 — Bit Manipulation ও Prefix Sums (5)

দুই সুপারপাওয়ার: bit দিয়ে O(1) trick, prefix দিয়ে O(1) range query।

#	Problem	Diff	Pattern / Skill	কেন জরুরি	Status
9	Count Set Bits	🟢	Brian Kernighan	flags, popcount	✅
10	Power of Two	🟢	n & (n-1)	capacity, hashmap sizing	✅
11	Single Number (XOR)	🟢	XOR cancel	dedupe, checksum	✅
12	Prefix Sum	🟢	prefix array	O(1) range sum, analytics	✅
13	Subarray Sum Equals K	🟡	prefix + hashmap	count ranges; super common	✅

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Stage 3 — Binary Search (incl. on answer) (5)

sorted-এ খোঁজা থেকে "উত্তরের উপর binary search" — একটি monotonic শর্তের সীমা খোঁজার কৌশল।

#	Problem	Diff	Pattern / Skill	কেন জরুরি	Status
14	Basic Binary Search	🟢	classic BS	সব search-এর ভিত্তি	✅
15	Lower / Upper Bound	🟡	boundary BS	DB index, std::lower_bound	✅
16	Square Root (BS)	🟢	BS on value	precision search	✅
17	Koko Eating Bananas	🟡	BS on answer	rate-limit/capacity tuning	✅
18	Allocate Minimum Pages	🔴	BS on answer + feasibility	load balancing, sharding	✅

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Stage 4 — Arrays ও Strings core (11)

interview-এর সবচেয়ে বড় ভাগ; এখানেই two-pointer, Kadane, prefix-product।

#	Problem	Diff	Pattern / Skill	কেন জরুরি	Status
19	Reverse String	🟢	two pointers	in-place basics	✅
20	Two Sum	🟢	hashmap complement	#1 interview problem	✅
21	Valid Anagram	🟢	frequency count	string fingerprint	✅
22	Move Zeroes	🟢	slow/fast pointer	in-place partition	✅
23	Best Time Buy/Sell Stock	🟢	running min	streaming min/max	✅
24	Maximum Subarray (Kadane)	🟡	Kadane DP	signal/profit windows	✅
25	Container With Most Water	🟡	two pointers	greedy discard	✅
26	Rotate Array	🟡	reversal trick	buffer/ring shift	✅
27	Product Except Self	🟡	prefix/suffix product	running aggregates	✅
28	3Sum	🟡	sort + two pointers	dedupe triples	✅
29	Longest Consecutive Sequence	🟡	hash set	O(n) without sort	✅

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Stage 5 — Hashing (5)

"আগে দেখেছি কিনা" — O(1) lookup-এর জাদু।

#	Problem	Diff	Pattern / Skill	কেন জরুরি	Status
30	Contains Duplicate	🟢	hash set	dedupe everywhere	✅
31	First Unique Character	🟢	frequency map	stream first-unique	✅
32	Missing Number	🟢	XOR/sum trick	integrity check	✅
33	Group Anagrams	🟡	canonical key bucket	grouping/indexing	✅
34	Top K Frequent Elements	🟡	count + heap/bucket	trending/analytics	✅

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Stage 6 — Two Pointers ও Sliding Window (6)

contiguous window — substring, rate, throughput সব এখানে।

#	Problem	Diff	Pattern / Skill	কেন জরুরি	Status
35	Longest Substring w/o Repeat	🟡	sliding window + set	dedupe window	✅
36	Minimum Size Subarray Sum	🟡	shrinkable window	min window meeting target	✅
37	At Most K Distinct	🟡	window + counts	"at most/exactly K" trick	✅
38	Minimum Window Substring	🔴	window + need-map	hard window mastery	✅
39	Trapping Rain Water	🔴	two pointers / prefix max	classic hard	✅
40	Sliding Window Maximum	🔴	monotonic deque	streaming max	✅

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Stage 7 — Stack ও Queue (7)

nesting, monotonic stack, "next greater" — parser ও scheduler-এর হাতিয়ার।

#	Problem	Diff	Pattern / Skill	কেন জরুরি	Status
41	Valid Parentheses	🟢	stack matching	parser/compiler basics	✅
42	Min Stack	🟡	aux stack	O(1) min design	✅
43	Queue via Stacks	🟢	amortized design	data-structure design	✅
44	Next Greater Element	🟡	monotonic stack	stock span, histograms	✅
45	Daily Temperatures	🟡	monotonic stack	wait-time problems	✅
46	Evaluate RPN	🟡	stack eval	expression engines	✅
47	Largest Rectangle in Histogram	🔴	monotonic stack	hard stack peak	✅

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Stage 8 — Linked List (7)

pointer surgery — reverse, cycle, merge; design (LRU)।

#	Problem	Diff	Pattern / Skill	কেন জরুরি	Status
48	Reverse Linked List	🟢	pointer rewiring	#1 LL skill	✅
49	Merge Two Sorted Lists	🟢	two-pointer merge	merge-sort building block	✅
50	Linked List Cycle	🟢	Floyd fast/slow	cycle detection	✅
51	Middle of List	🟢	fast/slow	split for merge-sort	✅
52	Remove Nth From End	🟡	two-pointer gap	one-pass delete	✅
53	Palindrome Linked List	🟡	reverse half	O(1) space check	✅
54	LRU Cache	🟡	hashmap + DLL design	real cache (Redis-style)	✅

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Stage 9 — Recursion ও Backtracking (7)

"সব সম্ভাবনা" তৈরি — subsets, permutations, grid search।

#	Problem	Diff	Pattern / Skill	কেন জরুরি	Status
55	Fibonacci (recursion→memo)	🟢	recursion + memo	DP-র গেটওয়ে	✅
56	Climbing Stairs	🟢	recurrence	counting paths	✅
57	Subsets	🟡	backtracking power set	combinations engine	✅
58	Permutations	🟡	backtracking + used	ordering/scheduling	✅
59	Combination Sum	🟡	backtracking + prune	choose-with-repeat	✅
60	Generate Parentheses	🟡	constrained backtracking	valid-config generation	✅
61	Word Search	🟡	grid DFS + backtrack	board/maze search	✅

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Stage 10 — Trees ও BST (10)

traversal, BFS/DFS, BST property, LCA, serialize — interview heartland।

#	Problem	Diff	Pattern / Skill	কেন জরুরি	Status
62	Maximum Depth	🟢	DFS recursion	tree recursion basics	✅
63	Inorder Traversal	🟢	DFS / stack	BST sorted order	✅
64	Invert Binary Tree	🟢	recursion	famous warm-up	✅
65	Symmetric Tree	🟢	mirror recursion	structural compare	✅
66	Level Order Traversal	🟡	BFS queue	layer processing	✅
67	Validate BST	🟡	bounds recursion	invariant checking	✅
68	Kth Smallest in BST	🟡	inorder + count	order statistics	✅
69	LCA of Binary Tree	🟡	post-order recursion	hierarchy queries	✅
70	Diameter of Binary Tree	🟡	height + global max	tree DP pattern	✅
71	Serialize/Deserialize Tree	🔴	DFS encode/decode	storage/transmission	✅

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Stage 11 — Heap / Priority Queue (5)

"top/kth/median" — streaming-এ সেরা।

#	Problem	Diff	Pattern / Skill	কেন জরুরি	Status
72	Kth Largest Element	🟡	min-heap size k	order statistics	✅
73	K Closest Points	🟡	heap by distance	nearest-neighbour	✅
74	Task Scheduler	🟡	greedy + heap	CPU/job scheduling	✅
75	Meeting Rooms II	🟡	heap of end-times	resource allocation	✅
76	Find Median from Data Stream	🔴	two heaps	streaming median	✅

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Stage 12 — Graphs (10)

BFS/DFS, topological sort, shortest path — সিস্টেম-চিন্তার মূল।

#	Problem	Diff	Pattern / Skill	কেন জরুরি	Status
77	Number of Islands	🟡	grid DFS/BFS	connected components	✅
78	Flood Fill	🟢	DFS/BFS	paint bucket, segmentation	✅
79	Rotting Oranges	🟡	multi-source BFS	spread/diffusion	✅
80	Clone Graph	🟡	DFS + hashmap	deep copy graphs	✅
81	Is Graph Bipartite	🟡	2-coloring BFS	conflict/grouping	✅
82	Course Schedule	🟡	cycle detect (topo)	dependency resolution	✅
83	Course Schedule II	🟡	topological order	build systems, DAG	✅
84	Word Ladder	🔴	BFS shortest path	transformation search	✅
85	Network Delay Time	🟡	Dijkstra	weighted shortest path	✅
86	Alien Dictionary	🔴	topo sort (hard)	ordering inference	✅

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Stage 13 — Union-Find / DSU (3)

"এরা কি একই দলে?" — connectivity-র দ্রুততম উত্তর।

#	Problem	Diff	Pattern / Skill	কেন জরুরি	Status
87	Redundant Connection	🟡	DSU cycle	network/tree validation	✅
88	Make Network Connected	🟡	DSU components	infra connectivity	✅
89	Accounts Merge	🔴	DSU + map	entity resolution/dedupe	✅

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Stage 14 — Dynamic Programming (11)

overlapping subproblems — interview-এর সবচেয়ে ভয়ের, কিন্তু pattern শিখলে সহজ।

#	Problem	Diff	Pattern / Skill	কেন জরুরি	Status
90	House Robber	🟡	1D DP	pick/skip pattern	✅
91	Unique Paths	🟡	grid DP	counting paths	✅
92	Minimum Path Sum	🟡	grid DP min	cost optimization	✅
93	Coin Change (min)	🟡	unbounded knapsack	make-change/optimization	✅
94	0/1 Knapsack (Book Shop)	🟡	0/1 knapsack	budget/resource picking	✅
95	Partition Equal Subset Sum	🟡	subset-sum DP	balancing/fairness	✅
96	Longest Increasing Subsequence	🟡	LIS DP	sequence trends	✅
97	Word Break	🟡	string DP	tokenization/parsing	✅
98	Longest Common Subsequence	🟡	2D DP	diff, DNA, similarity	✅
99	Edit Distance	🔴	2D DP	spellcheck, diff, fuzzy match	✅
100	Burst Balloons	🔴	interval DP	hardest DP class	✅

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🏁 Milestones

• Stage 1–3 শেষ (18): math + binary search ভিত্তি দখলে — অনেক easy interview এখনই পারবে।
• Stage 4–7 শেষ (47): arrays/strings/hashing/stack — job-ready interview-এর core।
• Stage 8–11 শেষ (76): LL + recursion + trees + heap — mid-level interview-ready।
• Stage 12–14 শেষ (100): graphs + DSU + DP — Google/FAANG on-site দেওয়ার মতো।

পরের ধাপ (এই path-এর সাথে যা চলবে)

• প্রতিদিন রুটিন: 2–4টা problem + আগেরগুলো দ্রুত review।
• প্রতি stage শেষে: pattern-টা নিজে এক প্যারায় লিখে ফেলা (note-এর "Pattern learned" দেখে)।
• System Design + behavioral (Google-এর জন্য) — DSA-র পাশাপাশি, web-dev roadmap-এর Phase 10-এ।

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নোট: এই 100-র প্রতিটা problem-এর .md-তে এখন Python + JavaScript + TypeScript solution + test cases + real-world use যোগ করা হয়ে গেছে — ১০০/১০০ ✅। সব JavaScript node-এ চলে (test pass), সব TypeScript tsc --strict-এ type-check pass — sandbox-এ স্বাধীনভাবে যাচাই করা।