我尝试过寻找与我类似的问题,但没有找到太多帮助。
我有这种结构的链表:
struct PCB {
struct PCB *next;
int reg1, reg2;
};
我首先以这种方式创建了10个PCB结构:
for(i=20;i<=30;i++) {
curr = (struct PCB *)malloc(sizeof(struct PCB));
curr->reg1 = i;
curr->next = head;
head = curr;
}
然后我需要再创建20个PCB结构,但需要使用reg1
生成rand()
值。我正在这样做:
for (j = 0;j<20;j++) {
curr = (struct PCB *)malloc(sizeof(struct PCB));
curr->reg1 = rand()%100;
curr->next = head;
head = curr;
}
但是,当将这些PCB结构插入到具有随机reg1
值的链表中时,我需要按顺序将它们插入到链表中(插入排序)。在单链接链表中处理此问题的最佳方法是什么?感谢
编辑: 我现在正在跟踪第一个创建的结构,以便能够从头开始遍历链表:
// create root struct to keep track of beginning of linked list
root = (struct PCB *)malloc(sizeof(struct PCB));
root->next = 0;
root->reg1 = 20;
head = NULL;
// create first 10 structs with reg1 ranging from 20 to 30
for(i=21;i<=30;i++) {
curr = (struct PCB *)malloc(sizeof(struct PCB));
// link root to current struct if not yet linked
if(root->next == 0){
root->next = curr;
}
curr->reg1 = i;
curr->next = head;
head = curr;
}
然后,当我创建另外10个需要插入排序的PCB结构时:
// create 20 more structs with random number as reg1 value
for (j = 0;j<20;j++) {
curr = (struct PCB *)malloc(sizeof(struct PCB));
curr->reg1 = rand()%100;
// get root for looping through whole linked list
curr_two = root;
while(curr_two) {
original_next = curr_two->next;
// check values against curr->reg1 to know where to insert
if(curr_two->next->reg1 >= curr->reg1) {
// make curr's 'next' value curr_two's original 'next' value
curr->next = curr_two->next;
// change current item's 'next' value to curr
curr_two->next = curr;
}
else if(!curr_two->next) {
curr->next = NULL;
curr_two->next = curr;
}
// move to next struct in linked list
curr_two = original_next;
}
head = curr;
}
但是这立即使我的计划崩溃了。
答案 0 :(得分:6)
“最佳”方式可能是为插入实现一个新功能。此函数将迭代列表,直到找到next
个节点值小于或等于要插入的节点的节点,然后将新节点放在next
节点之前。
这个功能怎么样:
void insert(struct PCB **head, const int reg1, const int reg2)
{
struct PCB *node = malloc(sizeof(struct PCB));
node->reg1 = reg1;
node->reg2 = reg2;
node->next = NULL;
if (*head == NULL)
{
/* Special case, list is empty */
*head = node;
}
else if (reg1 < (*head)->reg1)
{
/* Special case, new node is less than the current head */
node->next = *head;
*head = node;
}
else
{
struct PCB *current = *head;
/* Find the insertion point */
while (current->next != NULL && reg1 < current->next->reg1)
current = current->next;
/* Insert after `current` */
node->next = current->next;
current->next = node;
}
}
你会这样称呼:
insert(&root, rand() % 100, 0);
答案 1 :(得分:3)
以下是@Joachim的简化版本:
void insert(struct PCB **head, const int reg1, const int reg2)
{
struct PCB *new ;
/* Find the insertion point */
for ( ;*head; head = & (*head)->next)
{
if ((*head)->reg1 > reg1) break;
}
new = malloc(sizeof *new );
new->reg1 = reg1;
new->reg2 = reg2;
new->next = *head;
*head = new;
}
这个想法很简单:不需要任何特殊情况,无论如何: 需要更改指针,这可能是根指针,尾指针,或LL中间的一些指针。在任何/每种情况下:
->next
指针。