C語言指向結構體的指針進階：malloc 動態分配、嵌套結構體訪問、指向結構體數組指針的三種引用模式

指向結構體變量的指針：動態分配與嵌套訪問

struct data { int day, month, year; };
struct stu { char name[20]; long num; struct data birthday; };
main() {
    struct stu *student = malloc(sizeof(struct stu));
    scanf("%s", student->name);
    scanf("%ld", &student->num);
    scanf("%d%d%d", &student->birthday.year,
                  &student->birthday.month, &student->birthday.day);
    printf("%20s%10ld%10d//%d//%d\n",
           student->name, student->num,
           student->birthday.year, student->birthday.month, student->birthday.day);
}

• malloc 分配堆空間，sizeof 確保大小正確。
• 嵌套結構體成員用 student->birthday.year 逐級訪問。
• 箭頭運算符 -> 等價於 (*student).member。

指向結構體數組的指針：三種引用方式

定義 struct stu student[4], *p; p = student;

1. 地址法：(student+i)->member、(p+i)->member，等價 &student[i]。
2. 指針遞增法：p++ 移向下一元素，p->member 訪問。
3. 數組下標法：p[i].member，效果同 student[i].member。

完整輸出範例

struct stu *p, student[4] = {
    {"liying",1,{1978,5,23}}, {"wangping",2,{1979,3,14}},
    {"libo",3,{1980,5,6}}, {"xuyan",4,{1980,4,21}}
};
p = student;
for (int i=0;i<4;i++)
    printf("%20s%10ld%10d//%d//%d\n",
           (p+i)->name, (p+i)->num,
           (p+i)->birthday.year, (p+i)->birthday.month, (p+i)->birthday.day);

採用地址法 (p+i)-> 輸出四學生完整資料。