c - 将 qsort() 与结构一起使用

Question

我刚开始学习 C，对它还是个新手。在这个程序中，我正在处理一组结构。这些结构是:

typedef struct {
    int day;
    int month;
    int year;
} Date;

typedef struct {
    int serial_num;
    char full_name[15];
    Date *pDate;
} Person;

数组是Person *people。

现在我有两个人数组和这些人的出生日期(相同的索引):

const char* names[MAX] = { "Sasson_Sassoni", "Pooh", "James_Bond", "Elvis_is_Alive", "Shilgiya", "Cleopatra", "Sissoo_VeSimmhoo" };

const int dates[MAX][COLS] = {
        { 10, 1, 1988 },
        { 12, 12, 1948 },
        { 4, 12, 1970 },
        { 11, 11, 1890 },
        { 11, 11, 1948 },
        { 1, 10, 1213 },
        { 12, 11, 1948 }
    };

通过使用 switch case，每次用户键入 1 时，列表中的一个人(姓名和生日)都会添加到列表 people 中。然后，如果用户键入 3，则列表 people 应该按日期排序(从大到小)。所以我写了下面两个函数:

void sortList(Person **people, int index) {
    qsort(*people, index, sizeof(Person), intcmp);
}
int intcmp(const void *a, const void *b) {
    Person *one = (Person *)a;
    Person *two = (Person *)b;
    int year1 = one->pDate->year;
    int year2 = two->pDate->year;
    int month1 = one->pDate->month;
    int month2 = two->pDate->month;
    int day1 = one->pDate->day;
    int day2 = two->pDate->day;
    if (year1 > year2)
        return -1;
    else if (year2 > year1)
        return 1;
    if (month1 > month2)
        return -1;
    else if (month2 > month1)
        return 1;
    if (day1 > day2)
        return -1;
    else if (day2 > day1)
        return 1;
    return 0;
}

但每次我收到错误提示:

Exception thrown: read access violation.
one->pDate was nullptr.

有什么帮助吗？谢谢!

编辑:进一步解释:为了将人一个一个地插入到数组中，我创建了一个名为 index 的变量，每次添加一个人时，索引都会增加一个。所以在调用函数qsort()时，index就是数组中的人数。还有 MAX=7，COLS=3，LEN=10。将人添加到数组的函数是:

void addToList(Person **people, int *index, const char *names[MAX], const int dates[][COLS]) {
    people[*index] = (Person *)malloc(sizeof(Person));
    people[*index]->serial_num = *index + 1;
    strcpy(people[*index]->full_name, names[*index]);
    Date *temp = (Date *)malloc(sizeof(Date));
    temp->day = dates[*index][0];
    temp->month = dates[*index][1];
    temp->year = dates[*index][2];
    people[*index]->pDate = temp;
    printf("%d %s     %d/%d/%d \n", people[*index]->serial_num, people[*index]->full_name, people[*index]->pDate->day, people[*index]->pDate->month, people[*index]->pDate->year);
    *index = *index + 1;
}

Answer 1

您的 mcve 不完整，但我认为这是因为您混淆了指针和结构:

void sortList(Person **people, int index) {
    qsort(people, index, sizeof(Person *), intcmp);
    // or qsort(people, index, sizeof *people, intcmp);
}

int intcmp(const void *a, const void *b) {
    const Person *one = *(const Person **)a;
    const Person *two = *(const Person **)b;