如何为未知大小的结构动态分配内存？

void* malloc(size_t size);

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

typedef struct {
    int id;
    char name[20];
} Student;

int main() {
    int num;
    printf("请输入学生数量：");
    scanf("%d", &num);

    // 动态分配内存
    Student* students = (Student*)malloc(num * sizeof(Student));

    if (students == NULL) {
        printf("内存分配失败\n");
        return 1;
    }

    // 使用动态分配的内存
    for (int i = 0; i < num; i++) {
        printf("请输入第%d个学生的ID和姓名：", i + 1);
        scanf("%d %s", &(students[i].id), students[i].name);
    }

    // 释放内存
    free(students);

    return 0;
}

type* pointer = new type;

#include <iostream>

struct Student {
    int id;
    std::string name;
};

int main() {
    int num;
    std::cout << "请输入学生数量：";
    std::cin >> num;

    // 动态分配内存
    Student* students = new Student[num];

    // 使用动态分配的内存
    for (int i = 0; i < num; i++) {
        std::cout << "请输入第" << i + 1 << "个学生的ID和姓名：";
        std::cin >> students[i].id >> students[i].name;
    }

    // 释放内存
    delete[] students;

    return 0;
}