链表

反转链表

代码

class Solution {
    public ListNode reverseList(ListNode head) {
        ListNode next = null;
        ListNode pre = null;
        while(head != null) {
            next = head.next;
            head.next = pre;
            pre = head;
            head = next;
        }
        return pre;
    }
}

刷题

https://leetcode-cn.com/problems/reverse-linked-list/

精选题解

https://leetcode-cn.com/problems/fan-zhuan-lian-biao-lcof/solution/jian-zhi-offer-24-fan-zhuan-lian-biao-die-dai-di-2/

删除倒数第k个节点

代码

class Solution {
    public ListNode removeNthFromEnd(ListNode head, int n) {
        ListNode dummy = new ListNode(0, head);
        int length = getLength(head);
        ListNode cur = dummy;
        for (int i = 1; i < length - n + 1; ++i) {
            cur = cur.next;
        }
        cur.next = cur.next.next;
        ListNode ans = dummy.next;
        return ans;
    }

    public int getLength(ListNode head) {
        int length = 0;
        while (head != null) {
            ++length;
            head = head.next;
        }
        return length;
    }
}

刷题

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

精选题解

https://leetcode-cn.com/problems/remove-nth-node-from-end-of-list/solution/shan-chu-lian-biao-de-dao-shu-di-nge-jie-dian-b-61/

链表的中间结点

代码

class Solution {
    public ListNode middleNode(ListNode head) {
        ListNode slow = head, fast = head;
        while (fast != null && fast.next != null) {
            slow = slow.next;
            fast = fast.next.next;
        }
        return slow;
    }
}

刷题

https://leetcode-cn.com/problems/delete-middle-node-lcci/

精选题解

https://leetcode-cn.com/problems/middle-of-the-linked-list/solution/lian-biao-de-zhong-jian-jie-dian-by-leetcode-solut/

从尾到头打印链表

代码

class Solution {
    public int[] reversePrint(ListNode head) {
        Stack<ListNode> stack = new Stack<ListNode>();
        ListNode temp = head;
        while (temp != null) {
            stack.push(temp);
            temp = temp.next;
        }
        int size = stack.size();
        int[] print = new int[size];
        for (int i = 0; i < size; i++) {
            print[i] = stack.pop().val;
        }
        return print;
    }
}

刷题

https://leetcode-cn.com/problems/cong-wei-dao-tou-da-yin-lian-biao-lcof/

精选题解

https://leetcode-cn.com/problems/cong-wei-dao-tou-da-yin-lian-biao-lcof/solution/mian-shi-ti-06-cong-wei-dao-tou-da-yin-lian-biao-b/

删除链表的节点

代码

public void deleteNode(ListNode node) {
    node.val = node.next.val;
    node.next = node.next.next;
}

刷题

https://leetcode-cn.com/problems/delete-node-in-a-linked-list/

精选题解

https://leetcode-cn.com/problems/delete-node-in-a-linked-list/solution/shan-chu-lian-biao-zhong-de-jie-dian-by-leetcode/

链表中环的入口结点

代码

Set的使用

public class Solution {
    public ListNode detectCycle(ListNode head) {
        ListNode pos = head;
        Set<ListNode> visited = new HashSet<ListNode>();
        while (pos != null) {
            if (visited.contains(pos)) {
                return pos;
            } else {
                visited.add(pos);
            }
            pos = pos.next;
        }
        return null;
    }
}

快慢指针

public class Solution {
    public ListNode detectCycle(ListNode head) {
        ListNode fast = head, slow = head;
        while (true) {
            if (fast == null || fast.next == null) return null;
            fast = fast.next.next;
            slow = slow.next;
            if (fast == slow) break;
        }
        fast = head;
        while (slow != fast) {
            slow = slow.next;
            fast = fast.next;
        }
        return fast;
    }
}

刷题

https://leetcode-cn.com/problems/linked-list-cycle-ii/

精选题解

https://leetcode-cn.com/problems/linked-list-cycle-ii/solution/huan-xing-lian-biao-ii-by-leetcode-solution/

https://leetcode-cn.com/problems/linked-list-cycle-ii/solution/linked-list-cycle-ii-kuai-man-zhi-zhen-shuang-zhi-/

删除排序链表中的重复元素

代码

class Solution {
    public ListNode deleteDuplicates(ListNode head) {
        if (head == null) {
            return head;
        }
        
        ListNode dummy = new ListNode(0, head);

        ListNode cur = dummy;
        while (cur.next != null && cur.next.next != null) {
            if (cur.next.val == cur.next.next.val) {
                int x = cur.next.val;
                while (cur.next != null && cur.next.val == x) {
                    cur.next = cur.next.next;
                }
            } else {
                cur = cur.next;
            }
        }

        return dummy.next;
    }
}

刷题

https://leetcode-cn.com/problems/remove-duplicates-from-sorted-list-ii/

精选题解

https://leetcode-cn.com/problems/remove-duplicates-from-sorted-list-ii/solution/shan-chu-pai-xu-lian-biao-zhong-de-zhong-oayn/

两个链表的第一个公共节点

代码

public class Solution {
    public ListNode getIntersectionNode(ListNode headA, ListNode headB) {
        if (headA == null || headB == null) {
            return null;
        }
        ListNode pA = headA, pB = headB;
        while (pA != pB) {
            pA = pA == null ? headB : pA.next;
            pB = pB == null ? headA : pB.next;
        }
        return pA;
    }
}

刷题

https://leetcode-cn.com/problems/liang-ge-lian-biao-de-di-yi-ge-gong-gong-jie-dian-lcof/

精选题解

https://leetcode-cn.com/problems/liang-ge-lian-biao-de-di-yi-ge-gong-gong-jie-dian-lcof/solution/shuang-zhi-zhen-fa-lang-man-xiang-yu-by-ml-zimingm/

合并两个排序的链表

代码

class Solution {
    public ListNode mergeTwoLists(ListNode l1, ListNode l2) {
        ListNode dum = new ListNode(0), cur = dum;
        while(l1 != null && l2 != null) {
            if(l1.val < l2.val) {
                cur.next = l1;
                l1 = l1.next;
            }
            else {
                cur.next = l2;
                l2 = l2.next;
            }
            cur = cur.next;
        }
        cur.next = l1 != null ? l1 : l2;
        return dum.next;
    }
}

刷题

https://leetcode-cn.com/problems/he-bing-liang-ge-pai-xu-de-lian-biao-lcof/

精选题解

https://leetcode-cn.com/problems/he-bing-liang-ge-pai-xu-de-lian-biao-lcof/solution/

总结