c经典多级指针练习,写一个简单的集合

1:经典的指针习题,求打印结果

int main() {
    char *c[] = { "GULILAZHA", "LIYUCHUN", "LIUSHISHI", "ANJILA" };
    char **cp[] = { c + 3, c + 2, c + 1, c };
    char ***cpp = cp;
    printf("%s\n", **++cpp);
    printf("%s\n", *--*++cpp + 3);
    printf("%s\n", *cpp[-2] + 3);
    printf("%s\n", cpp[-1][-1] + 1);
    return 0;
}

结果执行是

LIUSHISHI
ILAZHA
ILA
IYUCHUN

首先画一下变量在内存中的位置

内存分布

++cpp,后cpp三级指针指向cp二级指针数组第一个也就是c+2的位置, *++cpp相当三级指针cpp取值得到二级指针c + 2 , c+2 相当一级指针数组c指向第二个, **++cpp, 相当再取值得到一级指针,也就是c+2当前所指向的值就是LIUSHISHI的地址,打印就是LIUSHISHI

--++cpp+3 同上道理, ++cpp三级指针再++指向二级指针数组第二个也就是c+1位置,取值得到二级指针c+1, --*++cpp后得到二级指针c, --++cpp相当再取值,得到一级指针c的首地址值也就是GULILAZHA的地址, --++cpp+3, 相当一级指针再右加三位打印就是ILAZHA

*cpp[-2] + 3 同上,cpp已经指向了第二个, cpp[-2],相当CPP指针回退2个步长后取值(三级指针指向的位置仍然没变),也就是二级指针c+3指向c指针数组第三个位置, *cpp[-2] 相当再取值得到一级指针也就是ANJILA, *cpp[-2] + 3再加3打印就是ILA

cpp[-1][-1] + 1 同上 cpp[-1]得到二级指针 c+2, 指向c指针数组第2个位置, cpp[-1][-1] , 相当取指向c指针数组第1个位置,得到一级指针LIYUCHUN的地址, cpp[-1][-1] + 1 , 加1打印相当就是IYUCHUN

2:实现一个简单的集合

typedef void Node;

typedef struct MyArrayList {
    int capacity;
    int length;
    int **nodes;//item指针数组(int* nodes[])
}MyArrayList;

MyArrayList* createList(int capacity);

int length(MyArrayList *list);

int add(MyArrayList *list, Node *node);

int addPosition(MyArrayList *list, Node *node, int position);

Node* get(MyArrayList *list, int position);

int remove(MyArrayList *list, int position);

int destory(MyArrayList *list);

MyArrayList* createList(int capacity) {
    MyArrayList *temp = (MyArrayList*) malloc(sizeof(MyArrayList));
    if (temp != NULL){
        temp->length = 0;
        temp->capacity = capacity;
        temp->nodes = (int**)malloc(sizeof(int*)* capacity);
    }   
    return temp;
}

int length(MyArrayList *list) {
    if (list != NULL) {
        return list->length;
    }
    return -1;
}

int add(MyArrayList *list, Node *node) {
    if (list == NULL || node == NULL) {
        return -2;
    }
    return addPosition(list, node, list->length);
}

int addPosition(MyArrayList *list, Node *node, int position) {
    if (list == NULL || node == NULL || position >= list->capacity || position < 0) {
        return -2;
    }
    if (list->length >= list->capacity) {
        printf("length=%d > capacity=%d", list->length, list->capacity);
        return -1;
    }
    for (int i = list->length - 1; i >= position; i--) {
        list->nodes[i + 1] = list->nodes[i];
    }
    list->length++;
    list->nodes[position] = (int *)node;
    return 1;
}

Node* get(MyArrayList *list, int position) {
    if (list == NULL) {
        return NULL;
    }
    if (position >= list->length) {
        printf("position %d outofbounds list length%d", position, list->length);
        return NULL;
    }
    return list->nodes[position];
}

int remove(MyArrayList *list, int position) {
    if (list == NULL || position < 0) {
        return -2;
    }
    if (position >= list->length) {
        printf("position %d outofbounds list length%d", position, list->length);
        return -1;
    }
    for (int i = position; i < list->length - 1; ++i) {
        list->nodes[i] = list->nodes[i + 1];
    }
    list->nodes[list->length - 1] = NULL;
    list->length--;
    return 1;
}

int destory(MyArrayList *list) {
    if (list == NULL) {
        return -2;
    }
    free(list->nodes);
    free(list);
    return 1;
}

int main() {
    MyArrayList *list = createList(10);
    Woman w1 = { 30, "安鸡拉" };
    Woman w2 = { 33, "刘湿湿" };
    Woman w3 = { 35, "滴力喇叭" };
    Woman w4 = { 19, "咕力拉扎" };
    Woman w5 = { 29, "李欲春" };

    add(list, &w1);
    add(list, &w2);
    add(list, &w3);
    addPosition(list, &w4, 1);
    add(list, &w5);
    
    return 0;
}

功能简单只是练习题而已,学过的东西偶尔拿出来练练,就不会忘记了