stack in c++ stl code example

Example 1: stack c++

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

Example 2: stack c++

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

Example 3: cpp stack

// Fast DIY Stack
template<class S, const int N> class Stack {
private:
    S arr[N];
    int top_i;

public:
    Stack() : arr(), top_i(-1) {}
    void push (S n) {
        arr[++top_i] = n;
    }
    void pop() {
        top_i--;
    }
    S top() {
        return arr[top_i];
    }
    S bottom() {
        return arr[0];
    }
    int size() {
        return top_i+1;
    }
};

Example 4: stack c++

#include <bits/stdc++.h> 

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