Question

我正在尝试为链表结构实现递归排序算法。 C语言。

我的算法是这样的： 1）在列表中找到最大值 2）将其从列表中删除并将其插入Head节点 3）从下一个节点再次启动算法 4）运行直到到达列表末尾

我有一些东西，但它没有“记住”我的清单。我意识到我在某个地方犯了错误（可能是递归调用），但我无法理解如何修复它。

typedef struct Node{
int data;
struct Node* next;
} Node;

void insert(Node** head, int val)
{
        //insert at top
        Node* to_insert = (Node*)malloc(sizeof(Node));
        to_insert->data = val;
        to_insert->next = (*head);
        (*head) = to_insert;
}

Node* sort_ll(Node* head)
{
    //base case, iterated trough entire list
    if(head == NULL)
        return NULL;

    int max = 0;
    Node* tmp = head;
    Node* to_move = tmp;

    //find maximum value
    while(tmp != NULL) {
        if(tmp->data > max) {
            max = tmp->data;
            to_move = tmp;
        }
        tmp = tmp->next;
    }

    //if its currently top, leave it there
    if(to_move == head) {
        return sort_ll(head->next);
    }

    //find node with max value
    tmp = head;
    while(tmp->next != to_move) {
        tmp = tmp->next;
    }

    //cut it out from the list
    tmp->next = tmp->next->next;
    free(to_move);

    //insert value at the head of the list
    insert(&head, max);

    return sort_ll(head->next);
}

int main()
{
    Node* list = NULL;

    insert(&list, 3);
    insert(&list, 6);
    insert(&list, 7);
    insert(&list, 2);
    insert(&list, 1);
    insert(&list, 5);
    insert(&list, 4);

    list = sort_ll(list);

    Node* tmp = list;

    while(tmp != NULL) {
        printf("%d\n", tmp->data);
        tmp = tmp->next;
    }


    return 0;
}

Answer 1

像这样修复

Node *sort_ll(Node* head){
    if(head == NULL || head->next == NULL)
        return head;//There is no need for processing

    int max = head->data;
    Node *prev = head;
    Node *to_move = NULL;
    Node *tmp = head->next;

    //find maximum value in rest(head->next)
    while(tmp != NULL) {
        if(tmp->data > max) {
            max = tmp->data;
            to_move = prev;//save previous node for remove link
        }
        prev = tmp;
        tmp = tmp->next;
    }

    if(to_move == NULL) {//not find in rest
        head->next = sort_ll(head->next);
        return head;
    }

    prev = to_move;
    to_move = prev->next;//max node
    prev->next = prev->next->next;//max node remove from link
    to_move->next = sort_ll(head);
    return to_move;
}

C：链表的递归排序

1 个答案: