#include <iostream> #include <iomanip> using namespace std; int num = 99; class A{ public: A(); private: int n; int &r; }; A::A(): n(0), r(num){} int main (){ A *a = new A(); cout<<sizeof(A)<<endl; //输出A类型的大小 cout<<hex<<showbase<<*((int*)a + 1)<<endl; //输出r本身的内容 cout<<&num<<endl; //输出num变量的地址 return 0; }

这段代码定义了一个类A，其中包含一个私有成员变量n和一个引用类型的私有成员变量r。在类的构造函数中，将n初始化为0，将r绑定到全局变量num上。在主函数中，通过new操作符创建类A的实例a，并输出了该类的大小、r本身的内容、以及全局变量num的地址。

需要注意的是，在输出r本身的内容时，将a强制转换为int指针类型，并将其加上1，是因为引用类型的成员变量实际上是一个指针，指向其所绑定的对象。所以a + 1实际上是指向r所绑定的num变量的地址。而输出num变量的地址时，则直接使用了&num操作符。

相关问题

#include <iostream> #include <string> #include <iomanip> using namespace std; class house{ private: string location; int num_of_rooms; int year_built; public: house(); house(string,int,int); void set_location(string); string get_location(); void set_num_of_rooms(int); int get_num_of_rooms(); void set_year_built(int); int get_year_built(); void print_house_details(); };

This is a class declaration for a `house` class with some private member variables and public member functions. Here is an example implementation for the `house_impl.cpp` file:

#include "house.h"

// Default constructor
house::house() {
    location = "";
    num_of_rooms = 0;
    year_built = 0;
}

// Parameterized constructor
house::house(string loc, int num, int year) {
    location = loc;
    num_of_rooms = num;
    year_built = year;
}

// Setter and getter functions for location
void house::set_location(string loc) {
    location = loc;
}

string house::get_location() {
    return location;
}

// Setter and getter functions for number of rooms
void house::set_num_of_rooms(int num) {
    num_of_rooms = num;
}

int house::get_num_of_rooms() {
    return num_of_rooms;
}

// Setter and getter functions for year built
void house::set_year_built(int year) {
    year_built = year;
}

int house::get_year_built() {
    return year_built;
}

// Function to print house details
void house::print_house_details() {
    cout << "Location: " << location << endl;
    cout << "Number of rooms: " << num_of_rooms << endl;
    cout << "Year built: " << year_built << endl;
}

Note that the implementation file should include the header file `house.h` which contains the declaration of the `house` class.

用C语言改一下#include<iostream> #include<cstring> #include<iomanip> using namespace std; struct student{ char name[20]; int num; //学号 int number; //票数 int Class; char major[30]; char grade[10]; char achievement[200]; }; class votesystem{ private: studentst; int count; //当前元素个数 int size; //哈希表长 public: void InitHashTable(int n); //初始化哈希表 int Hash(charname); //计算哈希地址 void collision(int &s); //冲突，计算下一个地址 int search(char name,int &s); //查找 void insert(charname); //插入 int vote(char*name); //投票 void display(); //显示哈希表 void showvote(int k); //按哈希表下标显示票数 void showrank(); //显示排行榜 };

使用C语言改写该代码如下：

#include <stdio.h>
#include <string.h>
#include <stdlib.h>

#define MAX_NAME_LEN 20
#define MAX_MAJOR_LEN 30
#define MAX_GRADE_LEN 10
#define MAX_ACHIEVEMENT_LEN 200
#define HASH_TABLE_SIZE 100

typedef struct student {
    char name[MAX_NAME_LEN];
    int num; //学号
    int number; //票数
    int Class;
    char major[MAX_MAJOR_LEN];
    char grade[MAX_GRADE_LEN];
    char achievement[MAX_ACHIEVEMENT_LEN];
} student;

typedef struct HashNode {
    student st;
    int flag; //标记该位置是否被占用
} HashNode;

typedef struct votesystem {
    HashNode table[HASH_TABLE_SIZE];
    int count; //当前元素个数
} votesystem;

void InitHashTable(votesystem *vs) {
    vs->count = 0;
    for (int i = 0; i < HASH_TABLE_SIZE; i++) {
        vs->table[i].flag = 0;
    }
}

int Hash(char *name) {
    int hash_val = 0;
    for (int i = 0; name[i] != '\0'; i++) {
        hash_val = (hash_val * 31 + name[i]) % HASH_TABLE_SIZE;
    }
    return hash_val;
}

void collision(int *s) {
    (*s)++;
    if (*s == HASH_TABLE_SIZE) {
        *s = 0;
    }
}

int search(votesystem *vs, char *name, int *s) {
    int hash_val = Hash(name);
    while (vs->table[hash_val].flag != 0 && strcmp(vs->table[hash_val].st.name, name) != 0) {
        collision(s);
        hash_val = Hash(name) + *s;
    }
    if (vs->table[hash_val].flag == 0) {
        return -1; //未找到该元素
    } else {
        return hash_val;
    }
}

void insert(votesystem *vs, student st) {
    if (vs->count == HASH_TABLE_SIZE) {
        printf("Hash table is full!\n");
    } else {
        int s = 0;
        int hash_val = Hash(st.name);
        while (vs->table[hash_val].flag == 1) {
            collision(&s);
            hash_val = Hash(st.name) + s;
        }
        vs->table[hash_val].st = st;
        vs->table[hash_val].flag = 1;
        vs->count++;
    }
}

int vote(votesystem *vs, char *name) {
    int s = 0;
    int hash_val = search(vs, name, &s);
    if (hash_val == -1) {
        printf("Student %s not found!\n", name);
        return -1;
    } else {
        vs->table[hash_val].st.number++;
        return vs->table[hash_val].st.number;
    }
}

void display(votesystem *vs) {
    for (int i = 0; i < HASH_TABLE_SIZE; i++) {
        if (vs->table[i].flag == 1) {
            printf("name: %s, num: %d, number: %d, Class: %d, major: %s, grade: %s, achievement: %s\n",
                   vs->table[i].st.name, vs->table[i].st.num, vs->table[i].st.number,
                   vs->table[i].st.Class, vs->table[i].st.major, vs->table[i].st.grade,
                   vs->table[i].st.achievement);
        }
    }
}

void showvote(votesystem *vs, int k) {
    if (k >= 0 && k < HASH_TABLE_SIZE && vs->table[k].flag == 1) {
        printf("name: %s, number: %d\n", vs->table[k].st.name, vs->table[k].st.number);
    } else {
        printf("Invalid index!\n");
    }
}

void showrank(votesystem *vs) {
    student *tmp_st = (student *) malloc(sizeof(student) * vs->count);
    int tmp_count = 0;
    for (int i = 0; i < HASH_TABLE_SIZE; i++) {
        if (vs->table[i].flag == 1) {
            tmp_st[tmp_count++] = vs->table[i].st;
        }
    }
    for (int i = 0; i < tmp_count - 1; i++) {
        for (int j = i + 1; j < tmp_count; j++) {
            if (tmp_st[i].number < tmp_st[j].number) {
                student tmp = tmp_st[i];
                tmp_st[i] = tmp_st[j];
                tmp_st[j] = tmp;
            }
        }
    }
    for (int i = 0; i < tmp_count; i++) {
        printf("%d. name: %s, number: %d\n", i + 1, tmp_st[i].name, tmp_st[i].number);
    }
    free(tmp_st);
}

int main() {
    votesystem vs;
    InitHashTable(&vs);
    student st1 = {"Tom", 1001, 0, 1, "Computer Science", "Grade 1", "Excellent"};
    student st2 = {"Jerry", 1002, 0, 1, "Computer Science", "Grade 1", "Good"};
    student st3 = {"Bob", 1003, 0, 1, "Computer Science", "Grade 1", "Average"};
    insert(&vs, st1);
    insert(&vs, st2);
    insert(&vs, st3);
    vote(&vs, "Tom");
    vote(&vs, "Jerry");
    vote(&vs, "Tom");
    vote(&vs, "Tom");
    display(&vs);
    showvote(&vs, Hash("Tom"));
    showrank(&vs);
    return 0;
}