数据结构重点内容

一.单链表

基于java实现：

// 节点类
class Node{int data;Node next;public Node(int data, Node next) {this.data = data;this.next = next;}public Node(int data){this.data = data;this.next = null;}
}
// 链表类
public class SinglyLinkedList {private Node head;public SinglyLinkedList() {head = null;}// 向链表结尾插入数据public void addNode(int data) {Node node = new Node(data);if (head == null) {head = node;}else {Node temp = head;while(temp.next != null) {temp = temp.next;}temp.next = node;}}// 获取链表长度public int length(){Node temp = head;int length = 0;while (temp != null) {length++;temp = temp.next;}return length;}// 删除下标为 n 的节点 ,这里假设头节点算第1个节点public boolean deleteNode(int n) {int length = length();if(n<1 || n>length) return false;if(n==1) {head = head.next;return true;}// 找到要删除节点的前一个节点Node temp = head;int count = 1;while(count<n-1) {count++;temp = temp.next;}// 删除节点（无论是中间节点还是尾节点）temp.next = temp.next.next;return true;}// 在不知道头节点的情况下删除指定节点public boolean deleteAnyNode(Node n){// 该节点为空或者是尾节点，就无法删除if(n==null || n.next==null) return false;// 将下一个节点的数据复制到当前节点n.data=n.next.data;// 跳过下一个节点（相当于删除了当前节点的数据）n.next = n.next.next;return true;}public void printList(){Node temp = head;while(temp!=null){System.out.print(temp.data+" ");temp = temp.next;}}// 链表反转,迭代法public Node reverseList(Node head){if(head==null || head.next==null) return head;Node prev = null;   // 前一个节点Node curr = head;   // 当前节点Node next = null;   // 下一个节点while(curr!=null){next = curr.next;   // 保存下一个节点curr.next = prev;   // 反转当前节点的指向 ,这一步是核心,上一步的顺序不能交换prev = curr;        // 移动prev指针curr = next;        // 移动current指针}head = prev;            // 反转后prev成为新的头节点return head;}// 寻找链表中间节点public Node findMid(Node head){if(head == null ) return null;Node fast = head;Node slow = head;// 如果长度为奇数，则fast在最后一个节点停下，若为偶数，则在倒数第二个节点停下while(fast.next!=null && fast.next.next!=null){fast = fast.next.next;slow = slow.next;}return slow;}// 查找链表倒数第k个元素public Node findK(Node head,int k){if(head == null || k<1) return null;Node fast = head;Node slow = head;for(int i=0;i<k;i++){// 如果k大于链表长度，提前返回空if(fast==null) return null;fast = fast.next;  // 快指针移动k步}while(fast!=null){   // 快慢指针之间应该相差k个节点，如k=2 slow在倒数第二个，则fast在尾节点之后（null）slow = slow.next;fast = fast.next;}return slow;}// 对链表排序,基于归并排序public void mergeSort(){head = mergeSort(head);}private Node mergeSort(Node head){// 空链表或单个链表无需排序if(head==null || head.next==null) return head;// 先找中间节点，用来拆分链表Node mid = findMid(head);Node rightHead = mid.next;// 切断链表mid.next = null;// 分别对左右两端链表递归调用Node left = mergeSort(head);Node right = mergeSort(rightHead);return merge(left,right);}// 合并两段链表private Node merge(Node left,Node right){Node res = new Node(0);Node curr = res;// 合并处理while(left!=null&&right!=null){if(left.data<right.data){curr.next = left;left = left.next;}else{curr.next = right;right = right.next;}curr = curr.next;}// 处理剩余节点if(left!=null){curr.next = left;}if(right!=null){curr.next = right;}return res.next;}// 删除链表的重复节点,保留1个节点，前提链表有序public void deleteDuplicates(Node head){if(head==null || head.next==null) return;Node curr = head;while(curr!=null && curr.next!=null){if(curr.data==curr.next.data){curr.next = curr.next.next;}else{curr = curr.next;}}}// 判断链表是否有环，如有则找到入口public boolean isLoop(Node head){Node fast = head;Node slow = head.next;while(fast!=slow){if(fast==null || fast.next==null) return false; // 能到末尾说明无环slow = slow.next;fast = fast.next.next;}return true;}// 确定有环，找到环的入口public Node findStart(Node head){// 先找到快慢指针第一次相遇的节点Node fast = head;Node slow = head;while(fast!=slow){slow = slow.next;fast = fast.next.next;}// 找到后将slow移动到头节点slow = head;while(slow!=fast){slow = slow.next;fast = fast.next;}return slow;}
}