简单学生成绩系统（类的练习2）

        单纯而又简单的练习，已经睁不开眼了。

#include <iostream>
#include <algorithm>
using namespace std;
class student{
public:
    struct node {
        string name;
        long long nums;
        int score;
        bool operator<(const node& a)const {
            return a.nums>nums;
        }
    };  
    student(int n = 0) {
        p = new node[n];
        temp = new node[n];
        len = 0;
    }//构造函数
    bool cmp(node x, node y) {
        return x.score < y.score;
    }
    void xinxi(long long n, string m, int w);
    void shuchu();
    void chaxun(int n); 
    node* p_get() {//得到p，因为你的p是私有的所以需要开一个接口调用，下面的len也是同理
        return p;
    }
    int len_get() { return len; }
private:
    node* p;
    node* temp;
    int len = 0;
};
void student::xinxi(long long n, string m, int w) {
    len++;
    temp = new node[len];//开辟新的内存空间
    for (int i = 0; i < len - 1; i++) {//全靠昨天葛葛的教诲
        temp[i].name = p[i].name;
        temp[i].nums = p[i].nums;
        temp[i].score = p[i].score;
    }
    temp[len - 1].nums = n;
    temp[len - 1].name = m;
    temp[len - 1].score = w;
    p = temp;
}
void student::shuchu() {
    for (int i = 0; i < len; i++) {
        cout << "学号：" << p[i].nums << "\t" << "姓名：" << p[i].name << "\t" << "成绩：" << p[i].score << endl;
    }
}
void student::chaxun(int n) {
    int ans = -1;
    int l = 0;
    int r = len;
    while (l <= r) {//就这事，葛葛非要我写个二分。当然要上我的万能模板了
        int mid = (l + r) / 2;
        if (p[mid].nums == n) {
            ans = mid;
            break;
        }
        else if (p[mid].nums < n) {
            l = mid + 1;
        }
        else {
            r = mid - 1;
        }
    }
    if (ans != -1) {
        cout << "该同学存在" << endl;
        cout << "姓名为：" << p[ans].name << " " << "成绩为：" << p[ans].score << endl;
    }
    else {
        cout << "不存在" << endl;
    }
}
void menu();
void input();
void output();
void lookup();
void cuowu();
student arr;
int main()
{   
    int n = -1;
    void menu();
    while(n!=4) {
        menu();
        cin >> n;
        switch(n)
        {
        case 1:input(); break;
        case 2:output(); break;
        case 3:lookup(); break;
        default:cuowu();break;
        }
    }
}
void menu() {
    cout << "输入1添加学生信息" << endl;
    cout << "输入2打印成绩表" << endl;
    cout << "输入3通过学号查询学生信息" << endl;
    cout << "输入4结束程序" << endl;
}
void input() {
    long long x; string y; int z;
    cout << "请输入学生学号：";
    cin >> x;
    cout << "请输入学生姓名：";
    cin >> y;
    cout << "请输入学生成绩：";
    cin >> z;
    arr.xinxi(x, y, z);
}
void output() {
    sort(arr.p_get(), arr.p_get() + arr.len_get());
    arr.shuchu();
}
void lookup() {
    sort(arr.p_get(), arr.p_get() + arr.len_get());
    int m;
    cout << "请输入您要查找的学号：";
    cin >> m;
    arr.chaxun(m);
    cout << endl;
}
void cuowu() {
    cout << "您输入的数字错误，请重新输入！" << endl;
}

         撒花！睡觉。