如何更改C函数中的结构变量？

struct Person {
    char name[20];
    int age;
};

struct Person p;
strcpy(p.name, "John");
p.age = 25;

// 更改结构变量的值
strcpy(p.name, "Tom");
p.age = 30;

struct Person {
    char name[20];
    int age;
};

struct Person p;
struct Person *ptr = &p;

// 更改结构变量的值
strcpy(ptr->name, "Tom");
ptr->age = 30;

struct Person {
    char name[20];
    int age;
};

void changePerson(struct Person *ptr) {
    strcpy(ptr->name, "Tom");
    ptr->age = 30;
}

struct Person p;

// 更改结构变量的值
changePerson(&p);