Things To Remember In Maps (Java)

This article helps you to recall the methods and classes of Maps and suggests you some leet code problems that you can start. And this article assumes that you have a basic understanding of the collection framework

K = datatype of Key

V = datatype of Vlaue

put(key , value )

keySet() -> returns Set data structure of all keys

get(key) -> returns value corresponding to the key

containsKey(key) -> true if the key is present else false

isEmpty()

remove(object key) -> removes the key-value pair and returns the value of the argument key

values()

clone() -> returns a shallow copy of the map

HashMap

LinkedHashMap: It maintains the insertion order

Data Structures Used: HashTable and LinkedList

TreeMap: It arranges the data in the sorted order considering the keys

Data Structure Used: Red-Black Tree (self-balancing binary search tree)

As TreeMap implements the NavigableMap Interface below are some of the methods which we can invoke with the object of treemap and I feel these are methods that are only mostly used.

firstEntry() -> returns MapEntry<K,V> (the first entry with kay and value which is least among all )

lastEntry() -> returns MapEntry<K , V> (obbesly it will be largest )

pollFirstEntry() -> returns MapEntry<K , V> (removes and returns the first entry )

pollLastEntry() -> returns MapEntry<K , V> (removes and returns the last entry )

subMap(K lowerBound , boolean include , K upperBound , boolean include )

-> returns NavigableMap<K , V >

ClassCastExecption

NullPointerExecption

IllegalArgumentExecption

Below are a few problems :

subarray-with-given-sum

longest-substring-without-repeating-characters

Count Distinct Elements in every Window of size k

find-missing-elements-of-a-range

check-if-an-array-can-be-divided-into-pairs-whose-sum-is-divisible-by-k

For Interview questions visit www.interviewbit.com

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Happy Coding.

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