Two Pointers — Pattern Recognition

1 Reverse array in-place Easy Arrays & Strings

Given an array a, reverse it in-place.

2 Left rotate array by k Easy Arrays & Strings

Given array a and integer k, return the left-rotated array.

4 Two sum (sorted array) Easy Arrays & Strings

Given sorted array a and target t, return indices of the pair that sums to t.

5 Check palindrome string Easy Arrays & Strings

Given string s, return True if it's a palindrome.

6 Merge two sorted arrays Easy Arrays & Strings

Given sorted arrays a and b, return a single merged sorted array.

11 Reverse a linked list Easy Linked Lists

Reverse a singly linked list in-place.

12 Detect cycle (Floyd's) Medium Linked Lists

Detect if a linked list has a cycle using O(1) space.

13 Find cycle start Medium Linked Lists

Find the node where the cycle begins in a linked list.

14 Find middle node Easy Linked Lists

Find the middle node of a linked list.

15 Merge two sorted lists Easy Linked Lists

Merge two sorted linked lists into one sorted list.

32 Merge two sorted arrays Easy Sorting

Merge two sorted arrays into one sorted array.

123 Container With Most Water Medium Two Pointers

Given n vertical lines, find two that form a container holding the most water.

124 Trapping Rain Water Hard Two Pointers

Given n non-negative integers representing an elevation map, compute how much water it can trap.

125 3Sum Medium Two Pointers

Given array nums, find all unique triplets that sum to zero.

126 Remove Duplicates from Sorted Array Easy Two Pointers

Given a sorted array, remove duplicates in-place and return the new length.