C++ HW12-1 for WallPower

請利用堆疊特性，寫出一程式，在使用者輸入一字串後，能反轉並輸出此字串。
參考結果如下。

#include <iostream>
#include <stdlib.h>
#include <string>
using namespace std;
#define NUM 100

class stack {
public:
 stack();
 void push(char);
 char pop();
 void printStack();
private:
 char array[NUM];
 char top;
};

stack::stack() {
 top = -1;
}
void stack::push(char n)
{
 if (top == NUM - 1) {
  cout << "stack is full!";
  exit(1);
 }
 array[++top] = n;
}
char stack::pop()
{
 if (top == -1) {
  cout << "stack is empty!!";
  exit(1);
 }
 return array[top--];
}
void stack::printStack()
{
 int i;
 if (top == -1) {
  cout << "stack is empty!!\n";
 }
 else {
  for (i = top; i >= 0; i--)
   cout << pop();
  cout << endl;
 }
}
int main(void)
{
 int choice = 0;
 string n;
 stack S1;
 while (true)
 {
  cin >> n;
  for (int i = 0; i < n.length(); i++)
   S1.push(n[i]);
  S1.printStack();
 }
 system("pause");
 return 0;
}