course2_week1_challenge.cpp

// Write functions that reverse the elements in a stack and in a queue. The starter code below include the STL <stack> and <queue> data structures.

// A stack of integers is declared as "std::stack<int>" and the stack's top() member function returns the integer at the top of the stack (but also 
// leaves it at the top of the stack). The push() method pushes a new integer onto the top of the stack and the pop() method deletes the value at the 
// top of the stack.

// A queue of integers is declared as "std::queue<int>" and the queue's front() member function returns the integer at the front of the queue (but also 
// leaves it at the front of the queue). The push() method pushes a new integer onto the back of the queue and the pop() method deletes the value at 
// the front of the queue.

// Your job is to implement procedures that reverse the order of elements in a stack, and in a queue. The procedures print_stack() and print_queue() 
// are provided to help you see if your procedures work.

#include <iostream>
#include <stack>
#include <queue>

std::stack<int> reverse_stack(std::stack<int> s) {
  std::stack<int> reversed_s;
  
  // write code here that returns a stack whose elements are
  // in reverse order from those in stack s
  while (!s.empty()) {
    reversed_s.push(s.top());
    s.pop();
  }
  
  return reversed_s;
}

std::queue<int> reverse_queue(std::queue<int> q) {
  std::queue<int> reversed_q;
  
  // write code here that returns a queue whose elements are
  // in reverse order from those in queue q
  std::stack<int> tmp;
  while (!q.empty()) {
    tmp.push(q.front());
    q.pop();
  }
  while (!tmp.empty()) {
    reversed_q.push(tmp.top());
    tmp.pop();
  }
  
  return reversed_q;
}

void print_stack(std::string name, std::stack<int> s) {
  std::cout << "stack " << name << ": ";
  while (!s.empty()) {
    std::cout << s.top() << " ";
    s.pop();
  }
  std::cout << std::endl;
}

void print_queue(std::string name, std::queue<int> q) {
  std::cout << "queue " << name << ": ";
  while (!q.empty()) {
    std::cout << q.front() << " ";
    q.pop();
  }
  std::cout << std::endl;
}

int main() {
  std::stack<int> s, rs;
  std::queue<int> q, rq;
  
  s.push(1); s.push(2); s.push(3); s.push(4); s.push(5);

  print_stack("s",s);

  rs = reverse_stack(s);

  print_stack("reversed s",rs);
  
  q.push(1); q.push(2); q.push(3); q.push(4); q.push(5);
  
  print_queue("q",q);
  
  rq = reverse_queue(q);
  
  print_queue("reversed q",rq);

  return 0;
}