Introduction

Stack is a data structure which provides Last In First Out (LIFO).

Stack is used in many places like in DFS traversal, and monotonic stack is used in many algos.

Sample Implementation of Stack using arrays

#include <iostream>
#include <vector>

using namespace std;

class Stack {
private:
  vector<int> storage;

public:
  Stack() : storage(vector<int>()) {}
  bool empty() { return storage.empty(); }
  void push(int val) {
    storage.push_back(val);
  }
  void pop() {
    storage.pop_back();
  }
  int top() {
    return storage.back();
  }
};

int main() {
  vector<int> aa = {10, 11, 12, 13, 14, 15};
  Stack st;
  for (int i : aa) st.push(i);

  while (!st.empty()) {
    cout << st.top() << " ";
    st.pop();
  }
  return 0;
}