Buy and Sell Stock (Maximum Profit)

Find the maximum profit from buying and selling stock with at most one transaction Read full solution .

Check if Array is Sorted

Determine if an array is sorted in ascending, descending, or not sorted at all Read full solution .

Find the Maximum Element in an Array

Find and return the largest element in an array of integers Read full solution .

Find Missing Number (1 to n)

Find the missing number in an array containing n distinct numbers taken from 1, 2, 3, ..., n+1 Read full solution .

Intersection of Two Arrays

Find the intersection of two arrays and return the result as an array Read full solution .

Find Majority Element (Boyer-Moore Algorithm)

Find the majority element that appears more than n/2 times using Boyer-Moore majority vote algorithm Read full solution .

Merge Two Sorted Arrays

Merge two sorted arrays into a single sorted array in-place Read full solution .

Move All Zeros to the End

Move all zeros in an array to the end while maintaining the relative order of non-zero elements Read full solution .

Reverse the order of elements in an array in-place and return the modified array Read full solution .

Find the Second Largest Element in an Array

Find and return the second largest element in an array of integers Read full solution .

Find two numbers in an array that add up to a target value Read full solution .

Find Duplicate Number

Find the duplicate number in an array containing n+1 integers where each integer is between 1 and n (inclusive) Read full solution .

Longest Consecutive Sequence

Find the length of the longest consecutive elements sequence Read full solution .

Maximum Subarray Sum (Kadane's Algorithm)

Find the contiguous subarray with maximum sum using Kadane's algorithm Read full solution .

Minimum Swaps to Sort Array

Find the minimum number of swaps required to sort an array Read full solution .

Product of Array Except Self

Return an array where each element is the product of all elements except itself Read full solution .

Rotate an array to the right by k steps Read full solution .

Sliding Window Maximum

Find the maximum element in each sliding window of size k Read full solution .

Subarray with Given Sum

Find a continuous subarray which adds to a given number Read full solution .

Three Sum (Triplets that Sum to Zero)

Find all unique triplets in the array which gives the sum of zero Read full solution .

Calculate how much rainwater can be trapped between bars of different heights Read full solution .

Arrays

Master array manipulation with fundamental problems covering searching, sorting, and advanced algorithms.

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QUESTION	DIFFICULTY
Buy and Sell Stock (Maximum Profit) Find the maximum profit from buying and selling stock with at most one transaction	Easy
Check if Array is Sorted Determine if an array is sorted in ascending, descending, or not sorted at all	Easy
Find the Maximum Element in an Array Find and return the largest element in an array of integers	Easy
Find Missing Number (1 to n) Find the missing number in an array containing n distinct numbers taken from 1, 2, 3, ..., n+1	Easy
Intersection of Two Arrays Find the intersection of two arrays and return the result as an array	Easy
Find Majority Element (Boyer-Moore Algorithm) Find the majority element that appears more than n/2 times using Boyer-Moore majority vote algorithm	Easy
Merge Two Sorted Arrays Merge two sorted arrays into a single sorted array in-place	Easy
Move All Zeros to the End Move all zeros in an array to the end while maintaining the relative order of non-zero elements	Easy
Reverse an Array Reverse the order of elements in an array in-place and return the modified array	Easy
Find the Second Largest Element in an Array Find and return the second largest element in an array of integers	Easy
Two Sum Find two numbers in an array that add up to a target value	Easy
Find Duplicate Number Find the duplicate number in an array containing n+1 integers where each integer is between 1 and n (inclusive)	Medium
Longest Consecutive Sequence Find the length of the longest consecutive elements sequence	Medium
Maximum Subarray Sum (Kadane's Algorithm) Find the contiguous subarray with maximum sum using Kadane's algorithm	Medium
Minimum Swaps to Sort Array Find the minimum number of swaps required to sort an array	Medium
Product of Array Except Self Return an array where each element is the product of all elements except itself	Medium
Rotate Array Rotate an array to the right by k steps	Medium
Sliding Window Maximum Find the maximum element in each sliding window of size k	Medium
Subarray with Given Sum Find a continuous subarray which adds to a given number	Medium
Three Sum (Triplets that Sum to Zero) Find all unique triplets in the array which gives the sum of zero	Medium
Trapping Rain Water Calculate how much rainwater can be trapped between bars of different heights	Hard

Overview

Arrays are one of the most fundamental data structures in computer science. This section covers essential array manipulation techniques, from basic operations to advanced algorithms.

Key Concepts

Array traversal and iteration
Two-pointer technique
Sliding window
Prefix sums
Sorting and searching
In-place modifications

Arrays

Overview

Key Concepts

Common Problems

Easy

Medium

Hard

Practice Tips

Resources