Insertion Sort List

Medium Sort a linked list using insertion sort. A graphical example of insertion sort. The partial sorted list (black) initially contains only the first element in the list. With each iteration one element (red) is removed from the input data and inserted in-place into the sorted list

Algorithm of Insertion Sort: Insertion sort iterates, consuming one input element each repetition, and growing a sorted output list. At each iteration, insertion sort removes one element from the input data, finds the location it belongs within the sorted list, and inserts it there. It repeats until no input elements remain.

Example 1: Input: 4->2->1->3 Output: 1->2->3->4

Example 2: Input: -1->5->3->4->0 Output: -1->0->3->4->5

题意

链表的插入排序，时间复杂度O(n^2)，空间复杂度O(1)

代码

/** * Definition for singly-linked list. * public class ListNode { * int val; * ListNode next; * ListNode(int x) { val = x; } * } */ class Solution { public ListNode insertionSortList(ListNode head) { ListNode cur = head, tail = head; while (cur != null) { // printList(head); cur = tail.next; if (cur == null) { break; } ListNode comp = head; while (comp != cur && comp.next != cur && comp.next.val < cur.val) { comp = comp.next; } if (comp.next == cur) { if (comp.val <= cur.val) { tail = cur; } else { // comp == head comp.next = cur.next; cur.next = comp; head = cur; } } else if (comp == head && head.val > cur.val) { tail.next = cur.next; cur.next = head; head = cur; } else { tail.next = cur.next; cur.next = comp.next; comp.next = cur; } } return head; } private void printList(ListNode head) { while (head != null) { System.out.print(head.val + ", "); head = head.next; } System.out.println(); } }