/*
* @Name: My Stack Implementation In Java
* @Author: Max Base
* @Date: 2022-10-31
* @Class: Data Structure, Dr. Mahsa Soheil Shamaee
*/
// Stack
class MyStack {
private int size;
private int top;
private int[] stack;
// Constructor
public MyStack(int size) {
this.size = size;
this.top = -1;
this.stack = new int[size];
}
// O(1)
// Push an element to the top of the stack and return true
// If the stack is full, throw an error and return false
public boolean push(int value) {
if (top == size - 1) {
System.out.println("Stack is full");
return false;
} else {
top++;
stack[top] = value;
return true;
}
}
// O(1)
// return -1 if stack is empty
// return top value if stack is not empty
// remove top value
public int pop() {
if (top == -1) {
System.out.println("Stack is empty");
return -1;
} else {
int value = stack[top];
top--;
return value;
}
}
// O(1)
// return -1 if stack is empty
// return top value if stack is not empty
// return top value without removing it
public int peek() {
if (top == -1) {
System.out.println("Stack is empty");
return -1;
} else {
return stack[top];
}
}
// O(1)
public boolean isEmpty() {
return top == -1;
}
// O(1)
public boolean isFull() {
return top == size - 1;
}
// O(1)
public int size() {
return top + 1;
}
public boolean resize(int newSize) {
if (newSize < size) {
System.out.println("New size is smaller than current size");
return false;
} else {
int[] newStack = new int[newSize];
for (int i = 0; i < size; i++) {
newStack[i] = stack[i];
}
stack = newStack;
size = newSize;
return true;
}
}
// O(n)
public void printStack() {
if (top == -1) {
System.out.println("Stack is empty");
} else {
System.out.println("Stack items:");
for (int i = top; i >= 0; i--) {
System.out.println(stack[i]);
}
}
}
}
// Example
public class HelloWorld {
public static void main(String []args){
System.out.println("Hello, World!");
MyStack stack = new MyStack(5);
stack.push(1);
stack.push(2);
stack.push(3);
stack.push(4);
stack.push(5);
stack.printStack();
System.out.println("Peek: " + stack.peek());
System.out.println("Pop: " + stack.pop());
System.out.println("Peek: " + stack.peek());
stack.printStack();
}
}