共享链栈（公用头节点）

#include<bits/stdc++.h>
using namespace std;

typedef struct Node{
	int data;
	struct Node *left;
	struct Node *right; 
}Node;

class LinkStack{
	private:
		Node *top;
	public:
		LinkStack();
		~LinkStack();
		void push(int x,string choice);
		int pop(string choice);
		int getTop(string choice);
		bool isEmpty(string choice); 
};

LinkStack::LinkStack()
{
	top=new Node;
	top->left=NULL;
	top->right=NULL;
}
LinkStack::~LinkStack()
{
	Node *q=top->left;
	Node *p; 
	while(q!=NULL){
		p=q->left;
		delete q;
		q=p;
	}
	
	Node *k=top->right;
	Node *l;
	while(k!=NULL){
		l=k->right;
		delete k;
		k=l;
	}
}
void LinkStack::push(int x,string choice)
{
	Node *q=new Node;
	if(choice=="left"){
		q->data=x;
		q->left=top->left;
		top->left=q; 
	}
	if(choice=="right"){
		q->data=x;
		q->right=top->right;
		top->right=q; 
	}
}
int LinkStack::pop(string choice)
{
	int x;
	if(choice=="left"){
		Node *q=top->left;
		if(!isEmpty(choice)){
			x=q->data;
			top->left=q->left;
			delete q;
			return x;
		}
	}
	if(choice=="right"){
		Node *q=top->right;
			if(!isEmpty(choice)){
			x=q->data;
			top->right=q->right;
			delete q;
			return x;
		}
	}
}
int LinkStack::getTop(string choice)
{
	if(choice=="left"){
		if(!isEmpty(choice)){
			return top->left->data;
		}
	}
	if(choice=="right"){
		if(!isEmpty(choice)){
			return top->right->data;
		}
	}
}
bool LinkStack::isEmpty(string choice)
{
	if(choice=="left"){
		if(top->left==NULL){
			return true;
		}
		else{
			return false;
		}
	}
	if(choice=="right"){
		if(top->right==NULL){
			return true;
		}
		else{
			return false;
		}
	}
}
int main()
{
	LinkStack T;
	int i,x;
	string choice;
	for(i=1;i<=10;i++){
		cin>>x>>choice;
		T.push(x,choice);
	}
	cout<<"左栈是否为空（空为1,非空为0):"<<T.isEmpty("left")<<endl;
	cout<<"左栈栈顶元素:"<<T.getTop("left")<<endl;
	cout<<"左栈出栈元素:"<<T.pop("left")<<endl; 
	cout<<"右栈是否为空（空为1,非空为0):"<<T.isEmpty("right")<<endl;
	cout<<"右栈栈顶元素:"<<T.getTop("right")<<endl;
	cout<<"右栈出栈元素:"<<T.pop("right")<<endl; 
	return 0;
}