Curated

CC-100

100 problems every Indian SDE must solve — curated for Flipkart, Amazon, Google, and top startups

Hash map pattern — asked everywhere

Best Time to Buy Stock

Sliding window variant, Flipkart favourite

Contains Duplicate

Set usage — warm-up problem

Product of Array Except Self

No division trick — Amazon SDE2

Maximum Subarray

Kadane's algorithm — asked at Zomato, Swiggy

Maximum Product Subarray

Kadane variant — tests DP intuition

Find Min in Rotated Sorted Array

Binary search variant — Google L3

Search in Rotated Sorted Array

Modified binary search — FAANG SDE1

Two-pointer on sorted — Paytm, Razorpay

Container With Most Water

Two pointer — Amazon OA favourite

Longest Substring Without Repeating

Sliding window — most common string problem

Longest Palindromic Substring

Expand around center — Microsoft, Google

Minimum Window Substring

Sliding window + freq map — FAANG hard

Freq count — every OA has this

Hash + sort key — Amazon, Flipkart

Encode and Decode Strings

Protocol design — system awareness

Valid Parentheses

Stack basics — every company screen

Generate Parentheses

Backtracking fundamentals

Daily Temperatures

Monotonic stack — PhonePe, Groww

Largest Rectangle in Histogram

Monotonic stack hard — Google, Amazon

Foundation — every DSA test

Binary SearchEasy

Search a 2D Matrix

2D binary search — Flipkart OA

Binary SearchMedium

Koko Eating Bananas

Binary search on answer — Google

Binary SearchMedium

Find Median From Data Stream

Two heaps — Amazon SDE2

Binary SearchHard

Reverse Linked List

Pointer manipulation — asked at every company

Linked ListEasy

Merge Two Sorted Lists

Merge logic — Microsoft, Infosys

Linked ListEasy

Linked List Cycle

Floyd's cycle detection — must know

Linked ListEasy

Reverse + merge — Google L3

Linked ListMedium

Remove Nth From End

Two pointer linked list — Amazon

Linked ListMedium

Merge K Sorted Lists

Heap merge — FAANG SDE2 classic

Linked ListHard

Invert Binary Tree

DFS warm-up — every tree section

Max Depth of Binary Tree

Recursion foundation

Structural comparison

Subtree of Another Tree

Recursive matching

Lowest Common Ancestor (BST)

LCA pattern — Google, Amazon

Level Order Traversal

BFS tree — most tree interviews start here

Validate Binary Search Tree

Inorder + bounds — Microsoft, Flipkart

Kth Smallest in BST

Inorder traversal — Amazon SDE1

Build Tree from Pre+Inorder

Tree reconstruction — Google

Binary Tree Max Path Sum

Global max in recursion — FAANG hard

Number of Islands

BFS/DFS on grid — asked everywhere

DFS + hashmap — Microsoft, Uber

Pacific Atlantic Water Flow

Multi-source BFS — Google

Course Schedule

Topological sort — Amazon, Flipkart

Connected Components

Union-Find pattern

BFS on implicit graph — Google

Network Delay Time

Dijkstra — Uber, Ola

Alien Dictionary

Topo sort on chars — FAANG SDE2

Climbing Stairs

DP intro — every company first DP round

Dynamic ProgrammingEasy

Unbounded knapsack — Flipkart, Paytm

Dynamic ProgrammingMedium

Longest Increasing Subsequence

Classic LIS — Google, Amazon

Dynamic ProgrammingMedium

DP + trie — Flipkart, Myntra

Dynamic ProgrammingMedium

Linear DP — fresher favourite

Dynamic ProgrammingMedium

House Robber II

Circular DP variant

Dynamic ProgrammingMedium

Longest Common Subsequence

2D DP — FAANG staple

Dynamic ProgrammingMedium

Grid DP — Amazon OA

Dynamic ProgrammingMedium

String DP — Google SDE2

Dynamic ProgrammingHard

Interval DP — FAANG senior

Dynamic ProgrammingHard

Top K Frequent Elements

Min-heap — Amazon, Flipkart

Kth Largest Element

Quickselect / heap — everywhere

Greedy + heap — Google, Uber

Merge + heap — system design thinking

Sort + overlap — Amazon OA

Merge Intervals

Interval merge — Flipkart, Paytm

IntervalsMedium

Non-Overlapping Intervals

Greedy interval — Google

IntervalsMedium

Insert Interval

Edge case heavy — Amazon SDE2

IntervalsMedium

Trie from scratch — Google, Microsoft

Trie + DFS — FAANG hard

Combination Sum

Backtrack template — standard

BacktrackingMedium

Recursion tree — Flipkart, Uber

BacktrackingMedium

Power set pattern

BacktrackingMedium

DFS + visited — Amazon, Microsoft

BacktrackingMedium

Classic backtrack — Google L4+

BacktrackingHard

Number of 1 Bits

Bit ops warm-up

Bit ManipulationEasy

DP + bits — Amazon

Bit ManipulationEasy

Sum of Two Integers

XOR + carry — Microsoft classic

Bit ManipulationMedium

XOR trick — OA staple

Bit ManipulationEasy

In-place matrix — Amazon, Flipkart

Matrix traversal — Microsoft OA

Set Matrix Zeroes

In-place with O(1) space

Trapping Rain Water

Two-pointer hard — FAANG SDE2 filter

Two PointersHard

Dutch national flag — Amazon

Two PointersMedium

Valid Palindrome

Two pointer warm-up

Two PointersEasy

Permutation in String

Anagram in window — Amazon, Flipkart

Sliding WindowMedium

Sliding Window Maximum

Deque pattern — Uber, Google

Sliding WindowHard

Longest Repeating Char Replacement

Sliding window + freq

Sliding WindowMedium

HashMap + DLL — FAANG SDE2 must

Auxiliary stack — Microsoft, Amazon

Queue Using Stacks

Two stack trick

Find the Duplicate Number

Floyd's in array — Google

Longest Consecutive Sequence

HashSet O(n) — Amazon, Flipkart

Greedy — OA staple

Greedy BFS — Google

Greedy invariant — Amazon

Hand of Straights

Greedy + sorting

Serialize/Deserialize BTree

Real-world encoding — Google SDE2