Arrays & Strings:

[11,22,33,44,55,66]

['a','b','c','d']

[object1, object2,..]

Types of Arrays:

i)1D array

ii)2D array

iii)MD array

arr[]

arr[][]

arr[][][][]

i)Traversal

ii)Searching(Finding the target element) - Linear Search or Sequential search / Binary Search

[11,22,33,44,55,66] - O(n)

max=66

min=11

K

Binary Search

Array - sorted

iii)Sorting

iv)Finding Max,Min,Sum, Average

Two Pointers Technique: Two pointers technique uses two indices(pointers)

to traverse a an array or string.

Direction of the pointers:

i)Opposite direction

ii)Same direction

iii)Fast and slow pointer

l --> <--r

[11,22,33,44,55,66]

l,r

[11,22,33,44,55,66]

l,r

[11,22,33,44,55,66]

Reversing, Pair sum, Sorted

Sliding Window

String or Array Problems : Nested for loops

O(n*n)

O(n)

Removing duplicates from a sorted array:

i)Brute force approach(nested loops)

ii)Two pointers technique

Sliding Window Approach:

i)Subarrays

ii)Substrings

iii)Continuous Range

A range - window - subsets of elements -

We maintain a window(subset) of elements and move it step-by-step

across the array/string, adjusting what changes.

Types:

i)fixed-sized window: the window size is fixed.

ii)variable-sized window: Windows size expands or shrinks based on

condition.

Maximum size subarray of size k

arr=[2,1,5,1,3,2]

Possible subarrays of size k = 3

{2,1,5} - 8

{1,5,1} - 7

{5,1,3} - 9

{1,3,2} - 6

String:

Reversing a string

01234

Hello - olleH

Palindrome -

Madam - madaM

Anagram Checking:

Two Strings with same characters and same frequency.

listen -

silent -

Longest word in a sentence

split("")