PriorityQueue

Basics

• Implements Queue

Construction

• By Comparator class:

PriorityQueue<Integer> pq = new PriorityQueue<>(new Comparator<Integer>(){

@Override

public int compare(Integer a, Integer b){

return a-b;

}

});

• By Lambda:

PriorityQueue<Integer> pq = new PriorityQueue<>((Integer a, Integer b) -> b-a);

Methods

Method	Runtime	Description	Return Type
add(E e)	O(log n)	Appends the specified element to the end of this list.	boolean
clear()	O(n)	removes all element	void
contains(Object o)	O(n) worst time	contains	boolean
iterator()	O(1)	creates a iterator	Iterator
offer(E e)	O(log n)	insert element (like add)	boolean
peek()	O(1)	retreves the head	E
poll()	O(n)	retrieves and remove the head	E
remove(Object o)	o(n)	removes a single instance of the specified value	boolean
size()	O(1)	return the size	int
toArray()/toArray(T[] a)	O(n)	return the array	[]/ T[]