Data Structures

Stack

Stack class from Collections Framework class can be used.

Creating

Stack<Integer> stack = new Stack<>();

Pushing

stack.push(i)

Popping

Integer i = stack.pop()

Peeking

Returns last element without removing.

Integer i = stack.peek()

Searching

Returns position of the element.

• Position starts from 1(not 0) and is counted from the topmost(last) element.
• Returns -1 if element is not found.

Integer pos = stack.search(element);

Heap

Heap is implemented using PriorityQueue in Java.

Creating

PriorityQueue<T> minHeap = new PriorityQueue<T>();

PriorityQueue<T> maxHeap = new PriorityQueue<T>(Collections.reverseOrder());

Inserting

heap.add(element);

Heapify

Adding elements from any collection or data structure to Priority Queue heapifies them.

heap.addAll(Arrays.stream(stones).boxed().toList());

Retrieval

For getting the top-most element without deleting.

heap.peek();

Delete

Deletes and returns the top-most element.

heap.poll();