stack c 2b 2b

1stack<int> stk;
2stk.push(5);
3int ans = stk.top(5); // ans =5
4stk.pop();//removes 5

1#include <iostream>
2using namespace std;
3int stack[100], n=100, top=-1;
4void push(int val) {
5   if(top>=n-1)
6   cout<<"Stack Overflow"<<endl;
7   else {
8      top++;
9      stack[top]=val;
10   }
11}
12void pop() {
13   if(top<=-1)
14   cout<<"Stack Underflow"<<endl;
15   else {
16      cout<<"The popped element is "<< stack[top] <<endl;
17      top--;
18   }
19}
20void display() {
21   if(top>=0) {
22      cout<<"Stack elements are:";
23      for(int i=top; i>=0; i--)
24      cout<<stack[i]<<" ";
25      cout<<endl;
26   } else
27   cout<<"Stack is empty";
28}
29int main() {
30   int ch, val;
31   cout<<"1) Push in stack"<<endl;
32   cout<<"2) Pop from stack"<<endl;
33   cout<<"3) Display stack"<<endl;
34   cout<<"4) Exit"<<endl;
35   do {
36      cout<<"Enter choice: "<<endl;
37      cin>>ch;
38      switch(ch) {
39         case 1: {
40            cout<<"Enter value to be pushed:"<<endl;
41            cin>>val;
42            push(val);
43            break;
44         }
45         case 2: {
46            pop();
47            break;
48         }
49         case 3: {
50            display();
51            break;
52         }
53         case 4: {
54            cout<<"Exit"<<endl;
55            break;
56         }
57         default: {
58            cout<<"Invalid Choice"<<endl;
59         }
60      }
61   }while(ch!=4);
62   return 0;
63}

1/* Stack is a data structure that provides two O(1) time operations:
2adding an element to the top and removing an element from the top.
3It is only possible to access the top element of a stack. */
4stack<int> s;
5s.push(3);
6s.push(2);
7s.push(5);
8cout << s.top(); // 5
9s.pop();
10cout << s.top(); // 2

1// Fast DIY Stack
2template<class S, const int N> class Stack {
3private:
4    S arr[N];
5    int top_i;
6
7public:
8    Stack() : arr(), top_i(-1) {}
9    void push (S n) {
10        arr[++top_i] = n;
11    }
12    void pop() {
13        top_i--;
14    }
15    S top() {
16        return arr[top_i];
17    }
18    S bottom() {
19        return arr[0];
20    }
21    int size() {
22        return top_i+1;
23    }
24};

1#include <bits/stdc++.h> 
2
3stack<int> stk;
4stk.push(5);
5int ans = stk.top(5); // ans =5
6stk.pop();//removes 5

1typedef struct Nodo{
2   Elem val;
3   struct Nodo *next;
4} *Stack;
5Stack Empty(){return NULL;}
6bool IsEmpty(Stack a){return a==NULL;}
7Elem Top(Stack a){return a->val;} 
8Stack Pop(Stack l){return l->next;}
9Stack Push(Elem x,Stack res){
10    Stack nuevo=(Stack)malloc(sizeof(struct Nodo));
11    nuevo->val=x;
12    nuevo->next=res;
13    return nuevo;
14}