线性表基本维护[ACM]

#include "iostream"
#include "string"
using namespace std;

typedef struct node{
    string data;
    struct node *next;
    node(string str){
        data=str;
        next=NULL;
    }

}Node;


    Node *head=new node("hfirst");
    Node *back=new node("bfirst");
    Node *current=NULL;
    Node *pre=head;


void add(string str){
    Node *temp;
    if(back->data=="bfirst")
        temp=new Node(str);
    else{
        temp=back->next;
        back->next=temp->next;
        temp->data=str;
        temp->next=NULL;
    }
    temp->next=head->next;
    head->next=temp;
    current=temp;
}

void move(int p){
    int i=0;
    for(;i<p;i++){
        pre=current;
        if(current==NULL){
            cout<<"worng!!!"<<endl;
            current=head->next;
            pre=head;
            break;
        }
        else
            current=current->next;
    }

}

void del(int i){
    Node *temp=current;
    Node*tp;
    while(i!=0&&current!=NULL){
        tp=current;
        current=current->next;
        i--;
    }
    if(current==NULL){
        
        back->next=pre->next;
        pre->next=NULL;
        pre=head;
        current=head->next;
    }
    else{
        pre->next=current;
        tp->next=NULL;
        temp->next=back->next;
        back->next=temp;
    }
    
}
void _print(){
    cout<<current->data;
}


void main(){
    string choice,str;
    int i;
    while(1){
    cin>>choice;
        if (choice==("ADD")){cin>>str;add(str);}
        if (choice==("MOVE")){cin>>i;move(i);}
        if (choice==("DEL")){cin>>i;del(i);}
        if (choice==("PRINT"))_print();
    }
    getchar();
}