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Curated practice path

Core Coding Interview Problems

Practice a carefully selected set of coding interview problems covering the essential data structures, algorithms, and patterns seen in technical interviews.

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DSA course

Learn the patterns, then solve the matching problems

Follow a structured path with short lessons, video classes when available, reference problems from this catalog, and progress that keeps your next step clear.

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Warm-Up

Build momentum while sharpening the fundamentals.

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Interview Core

Carefully selected problems covering essential interview patterns.

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Advanced Track

Demanding challenges that push your algorithmic reasoning further.

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Premium Track

Premium problems with solutions for deeper preparation.

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TopicType

Difficulty

Status

120 results across 20 topics in Interview Core

Arrays & Hashing

0/8 solved

Easy: 4Medium: 4

Solution

Count Elements With Maximum Frequency

Easy

Increment Submatrices by One

Medium

Maximum Side Length of a Square with Sum Less than or Equal to Threshold

Medium

N-Repeated Element in Size 2N Array

Easy

Number of Equivalent Domino Pairs

Easy

Special Positions in a Binary Matrix

Easy

Medium

Zero Array Transformation I

Medium

Two Pointers

0/6 solved

Medium: 6

Solution

Container With Most Water

Medium

Medium

Count the Number of Fair Pairs

Medium

Maximum Distance Between a Pair of Values

Medium

Minimum Time to Make Rope Colorful

Medium

Valid Triangle Number

Medium

Sliding Window

0/8 solved

Medium: 6Hard: 2

Solution

Check If a String Contains All Binary Codes of Size K

Medium

Count Subarrays With Fixed Bounds

Hard

Count Subarrays With Score Less Than K

Hard

Count the Number of Good Subarrays

Medium

Fruit Into Baskets

Medium

Longest Subarray of 1's After Deleting One Element

Medium

Maximum Erasure Value

Medium

Minimum Removals to Balance Array

Medium

Stack

0/7 solved

Medium: 5Hard: 2

Solution

Count Submatrices With All Ones

Medium

Maximal Rectangle

Hard

Maximum Score From Removing Substrings

Medium

Minimum Operations to Convert All Elements to Zero

Medium

Power Grid Maintenance

Medium

Replace Non-Coprime Numbers in Array

Hard

Using a Robot to Print the Lexicographically Smallest String

Medium

Binary Search

0/7 solved

Easy: 1Medium: 2Hard: 4

Solution

Find Smallest Letter Greater Than Target

Easy

Kth Smallest Product of Two Sorted Arrays

Hard

Last Day Where You Can Still Cross

Hard

Maximum Number of Tasks You Can Assign

Hard

Maximum Running Time of N Computers

Hard

Minimize the Maximum Difference of Pairs

Medium

Successful Pairs of Spells and Potions

Medium

Linked List

0/2 solved

Easy: 1Medium: 1

Solution

Convert Binary Number in a Linked List to Integer

Easy

Delete Nodes From Linked List Present in Array

Medium

Trees

0/7 solved

Easy: 2Medium: 4Hard: 1

Solution

Balance a Binary Search Tree

Medium

Balanced Binary Tree

Easy

Lowest Common Ancestor of Deepest Leaves

Medium

Maximum Level Sum of a Binary Tree

Medium

Maximum Number of K-Divisible Components

Hard

Maximum Product of Splitted Binary Tree

Medium

Sum of Root To Leaf Binary Numbers

Easy

Heap / Priority Queue

0/8 solved

Medium: 6Hard: 2

Solution

Find Minimum Time to Reach Last Room I

Medium

Maximum Average Pass Ratio

Medium

Maximum Number of Events That Can Be Attended

Medium

Meeting Rooms III

Hard

Minimum Cost Path with Edge Reversals

Medium

Minimum Number of Seconds to Make Mountain Height Zero

Medium

Swim in Rising Water

Hard

Two Best Non-Overlapping Events

Medium

Backtracking

0/6 solved

Easy: 1Medium: 4Hard: 1

Solution

Hard

Count Number of Maximum Bitwise-OR Subsets

Medium

Find Unique Binary String

Medium

Pyramid Transition Matrix

Medium

Sum of All Subset XOR Totals

Easy

The k-th Lexicographical String of All Happy Strings of Length n

Medium

Tries

0/1 solved

Hard: 1

Solution

Delete Duplicate Folders in System

Hard

Graphs

0/8 solved

Medium: 6Hard: 2

Solution

Check if There is a Valid Path in a Grid

Medium

Detect Cycles in 2D Grid

Medium

Find All People With Secret

Hard

Largest Color Value in a Directed Graph

Hard

Lexicographically Smallest Equivalent String

Medium

Minimize Hamming Distance After Swap Operations

Medium

Pacific Atlantic Water Flow

Medium

Snakes and Ladders

Medium

1-D Dynamic Programming

0/8 solved

Medium: 7Hard: 1

Solution

Bitwise ORs of Subarrays

Medium

Domino and Tromino Tiling

Medium

Largest Divisible Subset

Medium

Number of People Aware of a Secret

Medium

Number of Ways to Paint N × 3 Grid

Hard

Partition Equal Subset Sum

Medium

Solving Questions With Brainpower

Medium

Ways to Express an Integer as Sum of Powers

Medium

2-D Dynamic Programming

0/9 solved

Easy: 1Medium: 7Hard: 1

Solution

Count Square Submatrices with All Ones

Medium

Find the Maximum Length of Valid Subsequence II

Medium

Max Dot Product of Two Subsequences

Hard

Maximum Non Negative Product in a Matrix

Medium

Minimum ASCII Delete Sum for Two Strings

Medium

Minimum Score Triangulation of Polygon

Medium

Ones and Zeroes

Medium

Pascal's Triangle

Easy

Medium

Greedy

0/5 solved

Medium: 4Hard: 1

Solution

Hard

Divide Array Into Arrays With Max Difference

Medium

Longest Palindrome by Concatenating Two Letter Words

Medium

Minimum Domino Rotations For Equal Row

Medium

Partition Array Such That Maximum Difference Is K

Medium

Math & Geometry

0/10 solved

Easy: 1Medium: 9

Solution

Easy

Concatenation of Consecutive Binary Numbers

Medium

Construct Product Matrix

Medium

Count of Interesting Subarrays

Medium

Fraction to Recurring Decimal

Medium

Make Sum Divisible by P

Medium

Minimum Number of Operations to Make All Array Elements Equal to 1

Medium

Number of Zero-Filled Subarrays

Medium

Reordered Power of 2

Medium

Walking Robot Simulation

Medium

Bit Manipulation

0/5 solved

Easy: 4Medium: 1

Solution

Complement of Base 10 Integer

Easy

Easy

Easy

Smallest Number With All Set Bits

Easy

Smallest Subarrays With Maximum Bitwise OR

Medium

Design

0/6 solved

Medium: 6

Solution

Design a Food Rating System

Medium

Design Spreadsheet

Medium

Finding Pairs With a Certain Sum

Medium

Implement Router

Medium

Simple Bank System

Medium

Walking Robot Simulation II

Medium

Strings

0/6 solved

Medium: 6

Solution

Compare Version Numbers

Medium

Count Submatrices With Equal Frequency of X and Y

Medium

Minimum Penalty for a Shop

Medium

Medium

Remove Sub-Folders from the Filesystem

Medium

Unique Length-3 Palindromic Subsequences

Medium

Simulation

0/2 solved

Medium: 2

Solution

Count Unguarded Cells in the Grid

Medium

Diagonal Traverse

Medium

Sorting

0/1 solved

Medium: 1

Solution

Sort Matrix by Diagonals

Medium