1   #include <iostream>
 2    
 3    const int MAXSIZE = 100;
 4    
 5    class Stack{
 6    private:
 7        int array[MAXSIZE];
 8        unsigned int index = 0;
 9    public:
10    
11        void push(int val);
12        int pop();
13        int top();
14        unsigned int length();
15        void reset();
16    };
17    
18    void Stack::push(int val){
19        if(index < MAXSIZE){
20            array[index++] = val;
21        }   
22    }
23    int Stack::pop(){
24        if(index > 0){ 
25            return array[--index];
26        }   
27    }
28    int Stack::top(){
29        if(index!=0)
30            return array[index-1];
31    }
32    unsigned Stack::size(){
33        return index;
34    }
35    void reset(){
36       index = 0;
37    }

typedef struct node{
     int value;
     node* next;
 }node, *pnode;
 
 class Stack{
 private:
     pnode phead;
     unsigned int len = 0;
 public:
     Stack(){
         phead = NULL;
     }
     void push(int val);
     int pop();
     int top();
     bool isEmpty();
     unsigned int size();
     void reset();
     int operator[](const int index)const;
 };  
 
 void Stack::push(int val){
     if(phead){
         pnode temp = phead;
         phead = new node;
         phead->next = temp;
         phead->value = val;
     }   
     else{
         phead=new node;
         phead->value = val;
         phead->next = NULL;
     }   
     
     len++;
 }   
int Stack::pop(){
    int res = phead->value;
    pnode temp = phead;
    phead = phead->next;
    delete temp;
    len--;
    return res;
 }
 bool Stack::isEmpty(){
     return len==0;
 }
//return the length of the stack
 unsigned int Stack::size(){
     return len;
 }
 void Stack::reset(){
     while(len>0){
         pnode tmp = phead;
         phead=phead->next;
         delete tmp;
         len--;
     }
 }
//override the [] operator to access the stack like accessing an array
 int Stack::operator[](const int index)const{
     if(index >= len)
         return NULL;
     else{
         int i = len-1;
         pnode tmp = phead;
         while(i>index){
             tmp=tmp->next;
             i--;
         }
         return tmp->value;
     }
 }