01 — QUESTION BANK

Curated Questions.
Interview Ready.

300 handpicked LeetCode problems grouped by pattern for targeted interview preparation.

Easy48

Med196

Hard56

Patterns59

Showing 100 of 300 Problems

pattern 01

Arrays

10 problems

4 easy5 medium1 hard

0 / 10 Solved

Best Time to Buy and Sell Stock

EASY

Majority Element

EASY

Move Zeroes

EASY

Remove Duplicates from Sorted Array

EASY

Best Time to Buy and Sell Stock II

MEDIUM

Increasing Triplet Subsequence

MEDIUM

Number of Zero-Filled Subarrays

MEDIUM

Product of Array Except Self

MEDIUM

Rotate Array

MEDIUM

First Missing Positive

HARD

pattern 02

Strings

6 problems

3 easy2 medium1 hard

0 / 6 Solved

Is Subsequence

EASY

Longest Common Prefix

EASY

Valid Palindrome

EASY

Reverse Words in a String

MEDIUM

Zigzag Conversion

MEDIUM

Guess the Word

HARD

pattern 03

Linked List

10 problems

1 easy9 medium

0 / 10 Solved

Intersection of Two Linked Lists

EASY

Add Two Numbers

MEDIUM

Copy List with Random Pointer

MEDIUM

Design Linked List

MEDIUM

Flatten a Multilevel Doubly Linked List

MEDIUM

Partition List

MEDIUM

Remove Duplicates from Sorted List II

MEDIUM

Remove Nth Node From End of List

MEDIUM

Rotate List

MEDIUM

Swap Nodes in Pairs

MEDIUM

pattern 04

Stacks

8 problems

2 easy5 medium1 hard

0 / 8 Solved

Remove All Adjacent Duplicates In String

EASY

Valid Parentheses

EASY

Basic Calculator II

MEDIUM

Evaluate Reverse Polish Notation

MEDIUM

Min Stack

MEDIUM

Remove Duplicate Letters

MEDIUM

Removing Stars From a String

MEDIUM

Longest Valid Parentheses

HARD

pattern 05

Queues

3 problems

2 easy1 medium

0 / 3 Solved

Number of Recent Calls

EASY

Time Needed to Buy Tickets

EASY

Reveal Cards In Increasing Order

MEDIUM

pattern 06

Hash Tables

13 problems

6 easy7 medium

0 / 13 Solved

Contains Duplicate II

EASY

Design HashMap

EASY

Isomorphic Strings

EASY

Maximum Number of Balloons

EASY

Number of Good Pairs

EASY

Ransom Note

EASY

Encode and Decode TinyURL

MEDIUM

Group Anagrams

MEDIUM

Longest Consecutive Sequence

MEDIUM

Number of Good Ways to Split a String

MEDIUM

Number of Matching Subsequences

MEDIUM

Reorganize String

MEDIUM

Split Array into Consecutive Subsequences

MEDIUM

pattern 07

Prefix Sum

5 problems

1 easy4 medium

0 / 5 Solved

Range Sum Query - Immutable

EASY

Contiguous Array

MEDIUM

Continuous Subarray Sum

MEDIUM

Subarray Sum Equals K

MEDIUM

Subarray Sums Divisible by K

MEDIUM

pattern 08

Two Pointers

5 problems

1 easy3 medium1 hard

0 / 5 Solved

Merge Sorted Array

EASY

3Sum

MEDIUM

Container With Most Water

MEDIUM

Two Sum II - Input Array Is Sorted

MEDIUM

Trapping Rain Water

HARD

pattern 09

Fast and Slow Pointers

3 problems

2 easy1 medium

0 / 3 Solved

Happy Number

EASY

Middle of the Linked List

EASY

Linked List Cycle II

MEDIUM

pattern 10

Sliding Window - Fixed Size

5 problems

1 easy3 medium1 hard

0 / 5 Solved

Maximum Average Subarray I

EASY

Find All Anagrams in a String

MEDIUM

Maximum Sum of Distinct Subarrays With Length K

MEDIUM

Permutation in String

MEDIUM

Substring with Concatenation of All Words

HARD

pattern 11

Sliding Window - Dynamic Size

5 problems

4 medium1 hard

0 / 5 Solved

Longest Repeating Character Replacement

MEDIUM

Longest Substring Without Repeating Characters

MEDIUM

Max Consecutive Ones III

MEDIUM

Minimum Size Subarray Sum

MEDIUM

Minimum Window Substring

HARD

pattern 12

Kadane's Algorithm

4 problems

4 medium

0 / 4 Solved

Best Sightseeing Pair

MEDIUM

Maximum Product Subarray

MEDIUM

Maximum Subarray

MEDIUM

Maximum Sum Circular Subarray

MEDIUM

pattern 13

Recursion

3 problems

1 easy2 medium

0 / 3 Solved

Merge Two Sorted Lists

EASY

Decode String

MEDIUM

Pow(x, n)

MEDIUM

pattern 14

Binary Search

10 problems

1 easy7 medium2 hard

0 / 10 Solved

Search Insert Position

EASY

Find First and Last Position of Element in Sorted Array

MEDIUM

Find Minimum in Rotated Sorted Array

MEDIUM

Find Peak Element

MEDIUM

Koko Eating Bananas

MEDIUM

Random Pick with Weight

MEDIUM

Search a 2D Matrix

MEDIUM

Search in Rotated Sorted Array

MEDIUM

Find in Mountain Array

HARD

Median of Two Sorted Arrays

HARD

pattern 15

Bucket Sort

3 problems

3 medium

0 / 3 Solved

Maximum Gap

MEDIUM

Sort Characters By Frequency

MEDIUM

Top K Frequent Words

MEDIUM

pattern 16

Merge Sort

2 problems

1 medium1 hard

0 / 2 Solved

Sort List

MEDIUM

Reverse Pairs

HARD

pattern 17

QuickSort / QuickSelect

2 problems

2 medium

0 / 2 Solved

Kth Largest Element in an Array

MEDIUM

Sort Colors

MEDIUM

pattern 18

Divide and Conquer

3 problems

3 medium

0 / 3 Solved

Construct Quad Tree

MEDIUM

Convert Sorted List to Binary Search Tree

MEDIUM

Maximum Binary Tree

MEDIUM

Loading more… 100 of 300

01 — QUESTION BANK

Curated Questions.
Interview Ready.

300 handpicked LeetCode problems grouped by pattern for targeted interview preparation.

Easy48

Med196

Hard56

Patterns59

Showing 100 of 300 Problems

pattern 01

Arrays

10 problems

4 easy5 medium1 hard

0 / 10 Solved

Best Time to Buy and Sell Stock

EASY

Majority Element

EASY

Move Zeroes

EASY

Remove Duplicates from Sorted Array

EASY

Best Time to Buy and Sell Stock II

MEDIUM

Increasing Triplet Subsequence

MEDIUM

Number of Zero-Filled Subarrays

MEDIUM

Product of Array Except Self

MEDIUM

Rotate Array

MEDIUM

First Missing Positive

HARD

pattern 02

Strings

6 problems

3 easy2 medium1 hard

0 / 6 Solved

Is Subsequence

EASY

Longest Common Prefix

EASY

Valid Palindrome

EASY

Reverse Words in a String

MEDIUM

Zigzag Conversion

MEDIUM

Guess the Word

HARD

pattern 03

Linked List

10 problems

1 easy9 medium

0 / 10 Solved

Intersection of Two Linked Lists

EASY

Add Two Numbers

MEDIUM

Copy List with Random Pointer

MEDIUM

Design Linked List

MEDIUM

Flatten a Multilevel Doubly Linked List

MEDIUM

Partition List

MEDIUM

Remove Duplicates from Sorted List II

MEDIUM

Remove Nth Node From End of List

MEDIUM

Rotate List

MEDIUM

Swap Nodes in Pairs

MEDIUM

pattern 04

Stacks

8 problems

2 easy5 medium1 hard

0 / 8 Solved

Remove All Adjacent Duplicates In String

EASY

Valid Parentheses

EASY

Basic Calculator II

MEDIUM

Evaluate Reverse Polish Notation

MEDIUM

Min Stack

MEDIUM

Remove Duplicate Letters

MEDIUM

Removing Stars From a String

MEDIUM

Longest Valid Parentheses

HARD

pattern 05

Queues

3 problems

2 easy1 medium

0 / 3 Solved

Number of Recent Calls

EASY

Time Needed to Buy Tickets

EASY

Reveal Cards In Increasing Order

MEDIUM

pattern 06

Hash Tables

13 problems

6 easy7 medium

0 / 13 Solved

Contains Duplicate II

EASY

Design HashMap

EASY

Isomorphic Strings

EASY

Maximum Number of Balloons

EASY

Number of Good Pairs

EASY

Ransom Note

EASY

Encode and Decode TinyURL

MEDIUM

Group Anagrams

MEDIUM

Longest Consecutive Sequence

MEDIUM

Number of Good Ways to Split a String

MEDIUM

Number of Matching Subsequences

MEDIUM

Reorganize String

MEDIUM

Split Array into Consecutive Subsequences

MEDIUM

pattern 07

Prefix Sum

5 problems

1 easy4 medium

0 / 5 Solved

Range Sum Query - Immutable

EASY

Contiguous Array

MEDIUM

Continuous Subarray Sum

MEDIUM

Subarray Sum Equals K

MEDIUM

Subarray Sums Divisible by K

MEDIUM

pattern 08

Two Pointers

5 problems

1 easy3 medium1 hard

0 / 5 Solved

Merge Sorted Array

EASY

3Sum

MEDIUM

Container With Most Water

MEDIUM

Two Sum II - Input Array Is Sorted

MEDIUM

Trapping Rain Water

HARD

pattern 09

Fast and Slow Pointers

3 problems

2 easy1 medium

0 / 3 Solved

Happy Number

EASY

Middle of the Linked List

EASY

Linked List Cycle II

MEDIUM

pattern 10

Sliding Window - Fixed Size

5 problems

1 easy3 medium1 hard

0 / 5 Solved

Maximum Average Subarray I

EASY

Find All Anagrams in a String

MEDIUM

Maximum Sum of Distinct Subarrays With Length K

MEDIUM

Permutation in String

MEDIUM

Substring with Concatenation of All Words

HARD

pattern 11

Sliding Window - Dynamic Size

5 problems

4 medium1 hard

0 / 5 Solved

Longest Repeating Character Replacement

MEDIUM

Longest Substring Without Repeating Characters

MEDIUM

Max Consecutive Ones III

MEDIUM

Minimum Size Subarray Sum

MEDIUM

Minimum Window Substring

HARD

pattern 12

Kadane's Algorithm

4 problems

4 medium

0 / 4 Solved

Best Sightseeing Pair

MEDIUM

Maximum Product Subarray

MEDIUM

Maximum Subarray

MEDIUM

Maximum Sum Circular Subarray

MEDIUM

pattern 13

Recursion

3 problems

1 easy2 medium

0 / 3 Solved

Merge Two Sorted Lists

EASY

Decode String

MEDIUM

Pow(x, n)

MEDIUM

pattern 14

Binary Search

10 problems

1 easy7 medium2 hard

0 / 10 Solved

Search Insert Position

EASY

Find First and Last Position of Element in Sorted Array

MEDIUM

Find Minimum in Rotated Sorted Array

MEDIUM

Find Peak Element

MEDIUM

Koko Eating Bananas

MEDIUM

Random Pick with Weight

MEDIUM

Search a 2D Matrix

MEDIUM

Search in Rotated Sorted Array

MEDIUM

Find in Mountain Array

HARD

Median of Two Sorted Arrays

HARD

pattern 15

Bucket Sort

3 problems

3 medium

0 / 3 Solved

Maximum Gap

MEDIUM

Sort Characters By Frequency

MEDIUM

Top K Frequent Words

MEDIUM

pattern 16

Merge Sort

2 problems

1 medium1 hard

0 / 2 Solved

Sort List

MEDIUM

Reverse Pairs

HARD

pattern 17

QuickSort / QuickSelect

2 problems

2 medium

0 / 2 Solved

Kth Largest Element in an Array

MEDIUM

Sort Colors

MEDIUM

pattern 18

Divide and Conquer

3 problems

3 medium

0 / 3 Solved

Construct Quad Tree

MEDIUM

Convert Sorted List to Binary Search Tree

MEDIUM

Maximum Binary Tree

MEDIUM

Loading more… 100 of 300

Curated Questions.Interview Ready.

Arrays

Best Time to Buy and Sell Stock

Majority Element

Move Zeroes

Remove Duplicates from Sorted Array

Best Time to Buy and Sell Stock II

Increasing Triplet Subsequence

Number of Zero-Filled Subarrays

Product of Array Except Self

Rotate Array

First Missing Positive

Strings

Is Subsequence

Longest Common Prefix

Valid Palindrome

Reverse Words in a String

Zigzag Conversion

Guess the Word

Linked List

Intersection of Two Linked Lists

Add Two Numbers

Copy List with Random Pointer

Design Linked List

Flatten a Multilevel Doubly Linked List

Partition List

Remove Duplicates from Sorted List II

Remove Nth Node From End of List

Rotate List

Swap Nodes in Pairs

Stacks

Remove All Adjacent Duplicates In String

Valid Parentheses

Basic Calculator II

Evaluate Reverse Polish Notation

Min Stack

Remove Duplicate Letters

Removing Stars From a String

Longest Valid Parentheses

Queues

Number of Recent Calls

Time Needed to Buy Tickets

Reveal Cards In Increasing Order

Hash Tables

Contains Duplicate II

Design HashMap

Isomorphic Strings

Maximum Number of Balloons

Number of Good Pairs

Ransom Note

Encode and Decode TinyURL

Group Anagrams

Longest Consecutive Sequence

Number of Good Ways to Split a String

Number of Matching Subsequences

Reorganize String

Split Array into Consecutive Subsequences

Prefix Sum

Range Sum Query - Immutable

Contiguous Array

Continuous Subarray Sum

Subarray Sum Equals K

Subarray Sums Divisible by K

Two Pointers

Merge Sorted Array

3Sum

Container With Most Water

Two Sum II - Input Array Is Sorted

Trapping Rain Water

Fast and Slow Pointers

Happy Number

Middle of the Linked List

Linked List Cycle II

Sliding Window - Fixed Size

Maximum Average Subarray I

Find All Anagrams in a String

Maximum Sum of Distinct Subarrays With Length K

Permutation in String

Substring with Concatenation of All Words

Sliding Window - Dynamic Size

Curated Questions.
Interview Ready.

Curated Questions.
Interview Ready.