Stack

/*
    Time complexity: O(1)
    Space complexity: O(N)
  
    Where 'N' is the capacity of the stack.
*/

// Stack class.
class Stack {
  
public:
  
    // Declare array.
    vector<int> myStack;
  
    // Stack size.
    int stackSize;
  
    // Maximum size.
    int n;
  
    // Constructor function.
    Stack(int n) {
  
        // Initialize class objects.
        this -> myStack.resize(n);
        this -> stackSize = -1;
        this -> n = n;
    }

    // Push function.
    void push(int num) {
    
        // Check if stack is not full.
        if(stackSize != n - 1) {
        
            // Increment stack size and update array.
            ++stackSize;
            myStack[stackSize] = num;
        }
    }

    // Pop function.
    int pop() {

        // Check if stack is not empty.
        if(stackSize != -1) {
        
            // Decrease size and return element.
            --stackSize;
            return myStack[stackSize + 1];
        }
        else {
            return -1;
        }
    }
  
    // Top function.
    int top() {
    
        // Check if stack is not empty.
        if(stackSize != -1) {
        
            // Return element.
            return myStack[stackSize];
        }
        else {
            return -1;
        }
    }
  
    // To check whether stack is empty or not.
    int isEmpty() {
    
        // Check if stack is not empty.
        if(stackSize != -1) {
        
            // Return element.
            return 0;
        }
        else {
            return 1;
        }    
    }
  
    // To check whether stack is full or not.
    int isFull() {
    
        // Check if stack is not empty.
        if(stackSize != n - 1) {
        
            // Return element.
            return 0;
        }
        else {
            return 1;
        }    
    }
};