链表

• 设计链表

• 增加、删除

• 翻转

• 两两交换

• 链表相交

• 环形链表

删除链表

struct ListNode* removeElements(struct ListNode* head, int val) {
    
    struct ListNode* head_ptr = (struct ListNode*)malloc(sizeof(struct ListNode));

    head_ptr->next = head;

    struct ListNode* p = head_ptr;

    while(p->next != NULL)
    {
        if (p->next->val == val)
        {
            p->next = p->next->next;

            //free(temp);
        }
        else
            p = p->next;

    }

    //free(p);
    return head_ptr->next;
}

https://leetcode.cn/problems/remove-nth-node-from-end-of-list/

struct ListNode* removeNthFromEnd(struct ListNode* head, int n) {

    struct ListNode* head_ptr = (struct ListNode*)malloc(sizeof(struct ListNode));
    struct ListNode* p;
    head_ptr->next = head;
    p = head_ptr;

    int node_count = 0;

    while (p->next != NULL)
    {
        node_count++;
        p = p->next;
    }

    p = head_ptr;

    for (int i = 0; i<node_count-n; i++)
    {
        p = p->next;
    }

    p->next = p->next->next;
    return head_ptr->next;
}

struct ListNode* removeNthFromEnd(struct ListNode* head, int n) {

    struct ListNode* head_ptr = (struct ListNode*)malloc(sizeof(struct ListNode));

    head_ptr->next = head;
    struct ListNode* left = head_ptr;
    struct ListNode* right = head_ptr;

    int i;
    for (i=0; i<n; i++)
    {
        right = right->next;
    }

    while (right->next != NULL)
    {
        left = left->next;
        right = right->next;
    }

    left->next = left->next->next;
    return head_ptr->next;
}