Sorting Algorithms

A Sorting Algorithm is used to rearrange a given array or list of elements in an order. For example, a given array [10, 20, 5, 2] becomes [2, 5, 10, 20] after sorting in increasing order and becomes [20, 10, 5, 2] after sorting in decreasing order.

• There exist different sorting algorithms for different different types of inputs, for example a binary array, a character array, an array with a large range of values or an array with many duplicates or a small vs large array.
• The algorithms may also differ according to output requirements. For example, stable sorting (or maintains original order of equal elements) or not stable.
• Sorting is provided in library implementation of most of the programming languages. These sorting functions typically are general purpose functions with flexibility of providing the expected sorting order (increasing or decreasing or by a specific key in case of objects).

Basics

• Introduction to Sorting
• Applications of Sorting

Sorting Algorithms:

Comparison Based : Selection Sort, Bubble Sort, Insertion Sort, Merge Sort, Quick Sort, Heap Sort, Cycle Sort, 3-way Merge Sort
Non Comparison Based : Counting Sort, Radix Sort, Bucket Sort, TimSort, Comb Sort, Pigeonhole Sort
Hybrid Sorting Algorithms : IntroSort, Tim Sort

Library Implementations:

• qsort() in C
• sort() in C++ STL
• Arrays.sort() in Java with examples
• Collections.sort() in Java with Examples
• Sort a List in Python
• Sorting in JavaScript

Easy Problems

• Check if an array is Sorted
• Sort an array of two types
• Sort a String
• Sort Each Row of a Matrix
• Sort a Matrix
• Sort a Linked List
• Sort in Wave Form
• Sort by Frequency
• Sort from Different Machines
• Check if any two intervals overlap
• Missing elements of a range
• Sort by set bits counts
• Sort even and odd placed in different orders
• Sorting Big Integers
• Sort strings by lengths
• Merge Two Sorted Arrays
• Sort when two halves are sorted
• 2 Sum - Pair in a Sorted Array
• Intersection & Union of two Sorted
• Meeting Rooms
• K-th smallest after removing given Set

Medium Problems

• Minimum Increments to Make Unique
• Merge Overlapping Intervals
• Minimum Platforms
• Closest Pair of Points
• Chocolate Distribution Problem
• Min and Max Amount to Buy All
• Three Way Partitioning
• Sort an array of 0s, 1s and 2s
• Sort a linked list of 0s, 1s and 2s
• Inversion count
• K-th Smallest Element
• K Smallest Elements
• 3 Sum - Find Any
• 3 Sum - Closest Triplet
• Smallest Difference Triplet from Three arrays
• Merge K Sorted Arrays
• Merge K Sorted Linked Lists
• Min Unsorted Subarray to make array sorted
• Sort a nearly sorted array
• Sort n numbers in range from 0 to n^2 – 1
• Sort an array of 1 to n
• Sort according to order defined by another
• Maximum intervals overlap
• Permutation with worst Case of Merge Sort
• Permute two arrays such that all pair suns are greater than K
• Bucket Sort To Sort an Array with Negative Numbers
• 4 Sum - Find Any [More problems an 4 Sum are in Hard Section]

Hard Problems

• Merge Without Extra Space
• Top K Frequent Elements
• 3 Sum - Distinct Triplets
• 4 Sum - Distinct Quadruples
• 4 Sum - All Quadruples
• 4 Sum - Closest Quadruple
• Surpasser Counts in an Array
• Minimum consecutive number subsets
• Minimum swaps for Binary Tree to BST
• Max frequency diff
• Min swaps to reach given array
• Making Array Elements Same
• Sort after applying an equation
• Sorting strings without copying

Quick Links :

• ‘Practice Problems’ on Sorting
• Top Sorting Interview Questions
• ‘Quizzes’ on Sorting
• Learn Data Structure and Algorithms | DSA Tutorial