实验三双链表

#include <iostream>    
using namespace std;    
const int N=5;    
struct Std{    
    int date;    
    Std *next;    
}*p,*r;    
class Student{    
private:    
    Std *first;    
    int length;    
public:    
    Student();    
    Student(int a[],int n);    
    ~Student(){}    
    void Insert(int i,int x);    
    int Delete(int i);    
    int Get(int i);    
    int Locate(int x);    
    void Show();    
};    
Student::Student(){    
    first =new Std;    
    first->next=NULL;    
}    
Student::Student(int a[],int n){    
    first=new Std;    
    first->next=NULL;    
    r=first;    
    for (int i=0;i<n;i++){    
        p=new Std;    
        p->date=a[i];    
        r->next=p;    
        r=p;    
    }    
    r->next=NULL;    
    lenght=n;    
}    
void Student::Insert(int i,int x){    
    r=first;    
    int j=0;    
    while (r!=NULL&&j<i-1){    
        r=r->next;    
        j++;    
    }    
    if (r==NULL) throw "位置非法";    
    else {    
        p=new Std;    
        p->next=r->next;    
        p->date=x;    
        r->next=p;    
        length++;    
    }    
}    
int Student::Delete(int i){    
    r=first;    
    int j=0;    
    while (r!=NULL&&j<i-1){    
        r=r->next;    
        j++;    
    }    
    if (r==NULL) throw "位置非法";    
    else {    
        p=r->next;    
        r->next=p->next;    
        delete p;    
        lenght--;    
    }    
    return p->date;    
}    
int Student::Get(int i) {    
    r = first;    
    int j = 0;    
    while (r != NULL && j<i - 1) {    
        r = r->next;    
        j++;    
    }    
    if (r == NULL) throw "位置非法";    
    else     
        p = r;    
    return p->date;    
}    
int Student::Locate(int x) {    
    r = first;    
    int j=0;    
    while (r != NULL) {    
        r = r->next;    
        j++;    
        if (r->date == x) break;    
    }    
    if (r == NULL) throw "位置非法";    
    return j;    
}    
void Student::Show() {    
    r = first;    
    while (r->next!= NULL) {    
       #include <iostream>    
using namespace std;    
const int N = 5;    
struct Std {    
    int date;    
    Std *next,*prior;    
}*p, *r;    
class Student {    
private:    
    Std * first;    
    int length;    
public:    
    Student();    
    Student(int a[], int n);    
    ~Student() {}    
    void Insert(int i, int x);    
    int Delete(int i);    
    int Get(int i);    
    int Locate(int x);    
    int Getper(int x,int i);    
    void Show();    
};    
Student::Student() {    
    first = new Std;    
    first->next =first;    
    first->prior = first;    
}    
Student::Student(int a[], int n) {    
    first = new Std;    
    first->next = NULL;    
    r = first;    
    for (int i = 0; i<n; i++) {    
        p = new Std;    
        p->date = a[i];    
        r->next = p;    
        p->prior = r;    
        r = p;    
    }    
    r->next = first;    
    first->prior = r;    
    lenght = n;    
}    
void Student::Insert(int i, int x) {    
    r = first;    
    int j = 0,count = 0;    
    while (count<=length && j<i - 1) {    
        r = r->next;    
        count++;    
        j++;    
    }    
    if (count>length) throw "位置非法";    
    else {    
        p = new Std;    
        p->next = r->next;    
        r->next->prior = p;    
        r->next = p;    
        p->date = x;    
        p->prior = r;    
        length++;    
    }    
}    
int Student::Delete(int i) {    
    r = first;    
    int x,j = 0,count = 0;    
    while (count<=length && j<i - 1) {    
        r = r->next;    
        count++;    
        j++;    
    }    
    if (count>length) throw "位置非法";    
    else {    
        p = r->next;    
        p->next->prior = r;    
        r->next = p->next;    
        x = p->date;    
        delete p;    
    }    
    return x;    
}    
int Student::Get(int i) {    
r = first;    
    int j = 0,count = 0;    
    while (count<=length && j<i - 1) {    
        r = r->next;    
        count++;    
        j++;    
    }    
    if (count>length) throw "位置非法";    
    else    
        p = r->next;    
    return p->date;    
}    
int Student::Locate(int x) {    
    r = first;    
    int j = 0,count = 0;    
    while (count<=length) {    
        r = r->next;    
        count++;    
        j++;    
        if (r->date == x) break;    
    }    
    if (count>length) cout<<"找不到该数据"<<endl;    
    return j;    
}    
void Student::Show() {    
    r = first;    
    while (r->next != first) {    
        r = r->next;    
        cout << r->date << ' ';    
    }    
    cout << endl;    
}    
int Student::Getper(int x,int i){    
    r = first;    
    int j,count = 0;    
    while (count<=length) {    
        r = r->next;    
        count++;    
        if (r->date == x) break;    
    }    
    if (count>length) throw "找不到该数据";    
    if (i>length) throw "前移非法";    
    for (j=0;j<i;j++)    
        r=r->prior;    
    return r->date;    
}    
int main() {    
    int a[3] = { 75,85,95 };    
    try{    
    Student S(a, 3);    
    cout << "原表：" << endl;    
    S.Show();    
    cout << "在第3位插入98：" << endl;    
    S.Insert(1, 98);    
    cout << "插入后：" << endl;    
    S.Show();    
    cout << "删除第2位：" << endl;    
    S.Delete(2);    
    cout << "删除后：" << endl;    
    S.Show();    
    cout << "查75分的位置：" << endl;    
    cout<<S.Locate(75) <<endl;    
    cout<< "查第2位的成绩：" <<endl;    
    cout<< S.Get(2) << endl;    
    cout<< "查95分前2位的成绩：" <<endl;    
    cout<< S.Getper(95,2) << endl;    
    }    
    catch(char *s){    
        cout<<s<<endl;    
    }    
    return 0;    
}