关于链表的一些问题的整理
Posted 南风小斯
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链表的类通常表示如下:
public class ListNode { public int val; public ListNode next; public ListNode(int val, ListNode next=null) { this.val = val; this.next = next; } }
(一)创建链表
根据给定的数组使用尾插法和头插法创建链表
public static ListNode createListNode(int[] array) { ListNode node = new ListNode(array[0]); for (int i = 1; i < array.Length; i++) { addNode(node, array[i]); } return node; } private static void addNode(ListNode node, int val) { if (node.next == null) node.next = new ListNode(val); else addNode(node.next, val); }
public static ListNode headInsertNode(int[] array) { ListNode node = new ListNode(array[0]); for (int i = 1; i < array.Length; i++) { node = subHeadInsert(node, array[i]); } return node; } private static ListNode subHeadInsert(ListNode node, int val) { ListNode newNode = new ListNode(val); newNode.next = node; return newNode; }
(二)快慢指针的应用
public static ListNode findMidNode(ListNode node) { if (node == null || node.next == null || node.next.next == null) return node; ListNode slow = node; ListNode fast = node.next.next; while (fast != null) { slow = slow.next; fast = fast.next == null ? null : fast.next.next; } return slow; }
public static bool hasCycle(ListNode head) { if (head == null || head.next == null) return false; ListNode fast = head; ListNode slow = head; while(fast!=null && fast.next != null) { fast = fast.next.next; slow = slow.next; if (slow.Equals(fast)) return true; } return false; }
public static bool IsPalindrome(ListNode head) { if (head == null || head.next == null) return true; if (head.next.next == null) { if (head.val == head.next.val) return true; else return false; } ListNode slow = head; ListNode fast = head.next.next; Stack<int> values = new Stack<int>(); int flag = 0; while (fast != null) { values.Push(slow.val); slow = slow.next; if (fast.next == null) { fast = null; flag = 1; } else { fast = fast.next.next; } } if (flag == 0) values.Push(slow.val); while (slow != null && values.Count!=0) { slow = slow.next; int k = values.Pop(); if (slow.val != k) return false; } return true; }
public static ListNode removeNode(ListNode node, int val) { if (node == null) return null; if (node.val == val) return node.next; ListNode slow = node; ListNode fast = node; while (fast != null) { if (fast.val == val) { slow.next = fast.next; break; } else slow = fast; fast = fast.next; } return node; }
public static ListNode removeNthFromEnd(ListNode node, int n) { if (node == null && node.next == null) return null; ListNode slow = node; ListNode fast = node; while (n >= 0) { fast = fast.next; n--; } while (fast != null) { fast = fast.next; slow = slow.next; } slow.next = slow.next.next; return node; }
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