two pointers

Longest Palindromic Substring

Find the longest contiguous palindromic substring in a given string using dynamic programming and two-pointer expansion …

Container With Most Water

Find two vertical lines that can form a container with the most water in a given array of heights.

3Sum

Given an integer array, return all unique triplets where the sum is zero using two-pointer scanning with careful duplica…

3Sum Closest

Find the sum of three integers in an array that is closest to a given target using two-pointer scanning.

4Sum

The 4Sum problem requires finding all unique quadruplets in an array that sum to a specific target value.

Remove Nth Node From End of List

Remove the nth node from the end of a linked list using a two-pointer approach to solve efficiently.

Remove Duplicates from Sorted Array

Learn how to remove duplicates from a sorted array in-place using two-pointer scanning while preserving element order.

Remove Element

Remove Element challenges you to remove a value from an array in-place using efficient two-pointer scanning and tracking…

Find the Index of the First Occurrence in a String

Locate the first occurrence of a substring within a string using a two-pointer scanning strategy and invariant tracking …

Next Permutation

Next Permutation is a medium-difficulty problem focusing on generating the next lexicographically greater permutation of…

Trapping Rain Water

Calculate the total trapped rain water using the elevation map array, leveraging dynamic programming and two-pointer pat…

Rotate List

Rotate a singly linked list to the right by k positions using careful pointer manipulation and two-pointer traversal tec…

Sort Colors

Sort Colors requires in-place reordering of an array using a two-pointer scanning strategy to group 0s, 1s, and 2s effic…

Remove Duplicates from Sorted Array II

Solve the problem of removing duplicates from a sorted array in-place, ensuring each element appears at most twice, usin…

Remove Duplicates from Sorted List II

Remove duplicates from a sorted linked list, leaving only distinct values, and return the modified list in sorted order.

Partition List

Partition a linked list such that all nodes less than x come before nodes greater than or equal to x while preserving re…

Merge Sorted Array

Merge two sorted arrays into the first array in non-decreasing order, using a two-pointer approach.

Valid Palindrome

Check if a given string is a valid palindrome by using two-pointer scanning and invariant tracking techniques.

Linked List Cycle

Determine if a given linked list contains a cycle using pointer manipulation or hashing, focusing on detecting repeated …

Linked List Cycle II

Identify the start of a cycle in a linked list using pointer manipulation, efficiently handling edge cases without modif…

Reorder List

Reorder List requires careful pointer manipulation in a singly linked list to interleave nodes from the ends without alt…

Sort List

Sort List requires sorting a singly linked list efficiently using pointer manipulation and merge sort for optimal perfor…

Reverse Words in a String

Reverse Words in a String requires reordering words using precise two-pointer scanning with careful space handling for e…

Intersection of Two Linked Lists

Given two linked lists, find the node where they intersect or return null if they do not.