c - 指针和结构问题

Question

函数 find_young() 必须接收指针 p 作为实际参数。而p必须指向一个struct s，其中有最年轻的人。没有错误消息，但程序无法运行。请给我一些建议。

typedef struct
{
    char *name;
    int age;
} PERSON;

void find_young(PERSON **ip)
{
    PERSON s[3] = {{"John", 25}, {"Brandon", 28}, {"Alex", 30}};
    int i;
    int min = s[0].age; 
    for(i = 0; i < 3; i++)
    {
        if(min > s[i].age)
            **ip = s[i];
    }
}

int main()
{
    PERSON *p;
    find_young(&p);
    printf("The youngest person is %s.\n", p->name);
}

Answer 1

您需要对代码进行一些更改才能使其正常工作

---

1) 需要为struct分配内存，并为struct中的char* name分配内存

int main()
{
    PERSON *p = malloc(sizeof(PERSON));
    p->name = malloc(100);
    find_young(&p);
    printf("The youngest person is %s with age %d.\n", p->name, p->age);

    free(p->name);
    free(p);
}

---

2) 然后你需要将 name 和 age 值正确地复制到传递的 struct

void find_young(PERSON **ip)
{
    PERSON s[3] = {{"John", 25}, {"Brandon", 28}, {"Alex", 30}};
    int i;

    int min = s[0].age;             //copying the first value
    (**ip).age = s[0].age;
    strcpy((**ip).name, s[0].name);

    for(i = 1; i < 3; i++)          //starting from the next values to compare
    {
        if(min > s[i].age)
        {
            (**ip).age = s[i].age;
            strcpy((**ip).name, s[i].name);
        }
    }
}