为qsort的比较转换一个指向struct的指针

struct Person {
    char name[50];
    int age;
};

int compareByAge(const void* a, const void* b) {
    const struct Person* personA = (const struct Person*)a;
    const struct Person* personB = (const struct Person*)b;

    if (personA->age < personB->age) {
        return -1;
    } else if (personA->age > personB->age) {
        return 1;
    } else {
        return 0;
    }
}

struct Person persons[] = {
    {"Alice", 25},
    {"Bob", 30},
    {"Charlie", 20}
};

int numPersons = sizeof(persons) / sizeof(persons[0]);

qsort(persons, numPersons, sizeof(struct Person), compareByAge);