力扣labuladong——一刷day03

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前言

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一、力扣LCR 140. 训练计划 II

/**
 * 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 trainingPlan(ListNode head, int cnt) {
        ListNode p1 = head, p2;
        for(int i = 0; i < cnt; i ++){
            p1 = p1.next;
        }
        p2 = head;
        while(p1 != null){
            p1 = p1.next;
            p2 = p2.next;
        }
        return p2;
    }
}
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二、力扣LCR 142. 训练计划 IV

/**
 * 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 trainningPlan(ListNode l1, ListNode l2) {
        ListNode dump = new ListNode(-1, null), pre = dump;
        while(l1 != null && l2 != null){
            if(l1.val < l2.val){
                pre.next = l1;
                pre = pre.next;
                l1 = l1.next;
            }else{
                pre.next = l2;
                pre = pre.next;
                l2 = l2.next;
            }
        }
        if(l1 != null){
            pre.next = l1;
        }
        if(l2 != null){
            pre.next = l2;
        }
        return dump.next;
    }
}
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三、力扣LCR 171. 训练计划 V

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) {
 *         val = x;
 *         next = null;
 *     }
 * }
 */
class Solution {
    ListNode getIntersectionNode(ListNode headA, ListNode headB) {
        ListNode p1 = headA, p2 = headB;
        while(p1 != p2){
            if(p1 == null) p1 = headB;
            else p1 = p1.next;

            if(p2 == null) p2 = headA;
            else p2 = p2.next;
        }
        return p1;
    }
}
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四、力扣LCR 021. 删除链表的倒数第 N 个结点

/**
 * 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 removeNthFromEnd(ListNode head, int n) {
        ListNode p = new ListNode(-1,head);
        ListNode r = fun(p,n+1);
        r.next = r.next.next;
        return p.next;
    }
    public ListNode fun(ListNode head, int n){
        ListNode p = head;
        int i = 1;
        while(i < n){
            i ++;
            p = p.next;
        }
        ListNode res = head;
        while(p.next != null){
            p = p.next;
            res = res.next;
        }
        return res;
    }
}
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五、力扣LCR 022. 环形链表 II

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