Big O notation – leetcode cheat sheet

Big O notation cheat sheet provides the Big O notations for all data structures and algorithm including sorting, search, recursion, DFS and BFS, and memoization, Dynamic programming etc. The links are provided to download the jpg file of the cheat sheets. At the end, you can also download the Big O notation cheat sheet compilation in one poster.

Table of Content


Big O-Notation of Data Structures


Data structure

Access

Insert

Delete

Search

Traverse

Linear

Array

O(1)

O(1)

O(n)

O(n)

O(n)

Ordered array

O(1)

O(n)

O(n)

O(logn)

O(n)

Linked list

O(n)

O(1)

O(n)

O(n)

O(n)

Matrix

O(1)

O(1)

O(1)

O(m*n)

O(m*n)

Stack

O(1)

O(1)

O(1)

O(n)

O(n)

Queue

O(1)

O(1)

O(1)

O(n)

O(n)

Non-linear

Tree

O(n)

O(1)

O(n)

O(n)

O(n)

Balanced tree

O(logn)

O(logn)

O(logn)

O(logn)

O(n)

Graph

O(V)

O(1)

O(V+E)

O(V+E)

O(V+E)

Trie

O(s)

O(s)

O(s)

O(s)

O(n*s)

Suffix trie

O(s)

O(s)

O(s)

O(s)

O(s^2)

Download data structure cheat sheet


Big O-Notation of major Algorithms by categories


Algorithms

Time

Space

Used area

Sorting

Bubble, Selection, Insertion

O(n^2)

O(1)

Simple sort

Merge sort

O(n*logn)

O(n)

Stable sort

Quick sort

O(n*logn)

O(logn)

Quick sort

Searching

Linear search

O(n)

O(1)

Search in non-sorted array

Binary search

O(logn)

O(1)

Search in sorted array

Recursion

Factorial

O(n)

O(n)

Math

Valid parentheses

O(Cn)

O(Cn)

String

Permutation

O(n!)

O(n!)

Array, String

All subsets

O(2^n)

O(2^n)

Array, String

Dynamic Programming

Fibonacci

O(n)

O(1)

Math

Knapsack

O(n*w)

O(n*w)

Array

Edit distance

O(s*t)

O(t)

String

Num of unique paths in matrix

O(m*n)

O(n)

Matrix

Download algorithms cheat sheet


Big O-Notation of Sorting Algorithms


Sort

Best

Avg

Worst

Space

Stable

Bubble sort

O(n)

O(n^2)

O(n^2)

O(1)

Yes

Selection sort

O(n^2)

O(n^2)

O(n^2)

O(1)

No

Insertion sort

O(n)

O(n^2)

O(n^2)

O(1)

Yes

Merge sort

O(n*logn)

O(n*logn)

O(n*logn)

O(n)

Yes

Quick sort

O(n*logn)

O(n*logn)

O(n^2)

O(logn)

No

Download sorting cheat sheet


Big O-Notation leetcode cheat sheet in Recursions


Combinatorics

Sample questions

Formulas

Time

Permutations

Permutation of array

P(n, k) = n!/(n-k)!

O(P(n,k)), O(n!) when k=n

Combinations

Combination of range 1..n size k

C(n, k) =  n!/(n-k)!k!

O(C(n,k))

Combinations of subset

Combination of subset strings

C(m, n) = m^n

O(m^n)

All subsets

All subset of array 

C(2, n)= 2^n

O(2^n)

Catalan numbers

Generate valid parentheses

Cn = (2n)!/(n+1)!n!

O(Cn)

Download recursions cheat sheet


Big O-Notation leetcode cheat sheet in DFS and BFS


DFS and BFS use cases

Sample questions

Time

DFS in tree

Tree in-order traversal

O(n)

DFS in string without memo

Word break with recursion

O(2s)

DFS in string with memo

Word break with rec and memo

O(s2)

DFS in graph with memo

Graph DFS traversal

O(V+E)

DFS in matrix with memo

Number of island

O(m*n)

BFS in tree

Tree level order traversal

O(n)

BFS/Bi-directional BFS

in string with memo

Word ladder with memo

O(s*n)

BFS in graph with memo

Graph BFS traversal

O(V+E)

Find path with BFS in graph

Find path from src to dest

O(bd)

Find path with Bi-directional BFS

in graph

Find path with bi-directional BFS

O(bd/2)

Shortest path with BFS in

unweighted and undirected graph

Shortest path from src to dest

O(V+E)

Shortest path with BFS

in adjacent matrix

Shortest path between cells

O(m*n)

Download DFS and BFS cheat sheet


Big O-Notation of Java Collections


Java Collections APIs

Access

Insert

Delete

Search

Traverse

List

ArrayList

O(1)

O(1)

O(n)

O(n)

O(n)

LinkedList

O(n)

O(1)

O(n)

O(n)

O(n)

Stack

O(1)

O(1)

O(1)

O(n)

O(n)

Queue

ArrayDeque

O(1)

O(1)

O(1)

O(n)

O(n)

PriorityQueue

O(logn)

O(logn)

O(logn)

O(logn)

O(n)

Map

HashMap

O(1)

O(1)

O(1)

O(1)

O(n)

LinkedHashMap

O(1)

O(1)

O(1)

O(1)

O(n)

TreeMap

O(logn)

O(logn)

O(logn)

O(logn)

O(n)

Dictionary

Hashtable

O(1)

O(1)

O(1)

O(1)

O(n)

Set

HashSet

O(1)

O(1)

O(1)

O(1)

O(n)

LinkedHashSet

O(1)

O(1)

O(1)

O(1)

O(n)

TreeSet

O(logn)

O(logn)

O(logn)

O(logn)

O(n)

Download Java collections cheat sheet


Big O Notation Cheat Sheet poster


Big O Notation Cheat Sheet Poster

The Big O notation cheat sheet poster provides print version of all cheat sheets in one. The pages includes free download of web version.

What is leetcode cheat sheet?

The leetcode cheat sheet is the Big O notation (i.e. time complexity and space complexity) for the leetcode interview questions in data structures and algorithms, such as sorting, searching, recursion, dynamic programming, DFS and BFS etc.

O notation cheat sheet poster web

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