Generic Stack Using Resized Array And Iterator - Coursera Algorithms

To make the stack generic and to hide the internal representation of a stack from client, we can use Generics and Iterator.

Following is the program:

Generic Stack Using Linked List And Iterator - Coursera Algorithms

To make the stack generic and to hide the internal representation of a stack from client, we can use Generics and Iterator.

Following is the program:

Queue Using Array Resizing - Coursera Algorithms

Queues follow FIFO standard. To implement, we need to maintain two indices to first and last elements of the array, for enqueue and dequeue operations.

Following is the program:

Related Posts: 

Queue Using Linked List - Coursera Algorithms

Queue Using Linked List - Coursera Algorithms

Queues follow FIFO standard. To implement, we need to maintain two pointers to first and last nodes of linked list, as we insert at the end of the list and removed the first element of the list for enqueue and dequeue operations.

Following is the program:

Stack Using Array Resizing - Coursera Algorithms

When implementing stacks using arrays, we may run into overflow and underflow problems. We can resize the array on need basis by doubling the array in push op when the array has reached it's limit and by halving the array in pop op when the array is just 25% utilized. 

This will result in constant amortized time operations, but ~N in worst case.

Linked list on the other hand has constant time even in worst case. But still, linked list may take more time and memory because of the links. 

If occasional slow ops are bearable, then arrays would be a better option than linked lists. 

Following is the complete program:

Related Posts:  

Stack Using Linked List - Coursera Algorithms

Stack Using Array - Coursera Algorithms

Stack Using Array - Coursera Algorithms

Stack works in a LIFO order. It supports insert, remove, iteration and test for empty operations.

They can be represented using array. An initial capacity for this array is taken as input. We manipulate an index variable for push and pop, instead of actually deleting items from stack.

If using objects in stack, avoid loitering(holding references to objects and preventing GC) by using following code in pop operation:

public String pop() { String item = s[--N]; s[N] = null; return item; } 

Following is the complete program:

Related Posts:  

Stack Using Linked List - Coursera Algorithms

Stack Using Linked List - Coursera Algorithms

Stack works in a LIFO order. It supports insert, remove, iteration and test for empty operations.

They can be represented using linked list. Push and pop operations are done on the first element. This takes constant time for any operation and about ~36N Bytes for N stack items - 16B overhead + 8B inner Node class + 8B reference to Node object + 4B for integer values.

Following is the program: