[数据结构与算法]2021-12-31 61. 旋转链表 141. 环形链表 83. 删除排序链表中的重复元素

61. 旋转链表

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode() {}
 *     ListNode(int val) { this.val = val; }
 *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
 * }
 */
class Solution {
    public ListNode rotateRight(ListNode head, int k) {
        if(head==null || head.next==null){
            return head;
        }
        //难点：在于成环，怎么断环
        ListNode cur=head;
        int n=0;
        while(cur!=null){
            n++;
            cur=cur.next;
        }
        ListNode c=head;
        for(int i=0;i<n-1;i++){
            c=c.next;
        }
        //成环
        c.next=head;
        k=k%n;
        ListNode res=head;
        for(int i=0;i<n-k;i++){
            cur=res;
            res=res.next;
        }
        cur.next=null;
        return res;
    }
}

141. 环形链表

/**
 * Definition for singly-linked list.
 * class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) {
 *         val = x;
 *         next = null;
 *     }
 * }
 */
public class Solution {
    public boolean hasCycle(ListNode head) {
        if(head==null || head.next==null) return false;
        ListNode slow=head;
        ListNode fast=head;
        while(fast!=null && fast.next!=null){
            fast=fast.next.next;
            slow=slow.next;
             if(slow==fast){
                return true;
            }
        }
        return false;
    }
}

83. 删除排序链表中的重复元素

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode() {}
 *     ListNode(int val) { this.val = val; }
 *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
 * }
 */
class Solution {
    public ListNode deleteDuplicates(ListNode head) {
        if(head==null || head.next==null) return head;
        ListNode cur=head.next;
        ListNode temp=head;
        while(cur!=null){
            if(cur.val==temp.val){
                temp.next=temp.next.next;
                cur=temp.next;
            }else{
                temp=cur;
                cur=cur.next;
            }
        }
    return head;

    }
}