insertion sort not quite understand

最新推荐文章于 2022-10-05 15:13:28 发布

转载最新推荐文章于 2022-10-05 15:13:28 发布 · 766 阅读

本文介绍了一种基于链表实现的插入排序算法。通过创建一个虚拟头节点，并遍历输入链表，将每个节点插入到已排序的部分中正确的位置。这种方法保持了插入排序的基本思想，同时适用于链表数据结构。

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/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) {
 *         val = x;
 *         next = null;
 *     }
 * }
 */
public class Solution {
    public ListNode insertionSortList(ListNode head) {
        // IMPORTANT: Please reset any member data you declared, as
        // the same Solution instance will be reused for each test case.
        if(head == null || head.next==null){
            return head;
        }
        ListNode dummyHead = new ListNode(-2147483648);
        //dummyHead.next = head;
        ListNode p1 = dummyHead, p2 = head;
        
        while(p2 != null){
            ListNode pre = findInsertPlace(p1, p2);
            // insert into list
            // save orignal list next node
            ListNode originalNext = p2.next;
            p2.next = pre.next;
            pre.next = p2;
            
            p2 = originalNext;
        }
        
        return dummyHead.next;
    }
    
    public ListNode findInsertPlace(ListNode p1, ListNode p2){
        ListNode pre = null, cur = p1;
        while(cur != null && cur.val <= p2.val){
            pre = cur;
            cur = cur.next;
        }
        return pre;
    }
}