lintcode-easy-Insertion Sort List

Sort a linked list using insertion sort.

Example

Given 1->3->2->0->null, return 0->1->2->3->null.

 

思路也比较直接，insertion sort，要注意的就是操作linkedlist的一些问题

 

/**
 * Definition for ListNode.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int val) {
 *         this.val = val;
 *         this.next = null;
 *     }
 * }
 */ 
public class Solution {
    /**
     * @param head: The first node of linked list.
     * @return: The head of linked list.
     */
    public ListNode insertionSortList(ListNode head) {
        // write your code here
        
        if(head == null || head.next == null)
            return head;
        
        ListNode fakehead = new ListNode(0);
        fakehead.next = head;
        
        ListNode prev = head;
        ListNode curr = head.next;
        
        while(curr != null){
            if(curr.val > prev.val){
                prev = curr;
                curr = curr.next;
            }
            else{
                ListNode p = fakehead;
                while(p != prev && p.next.val < curr.val)
                    p = p.next;
                prev.next = curr.next;
                curr.next = p.next;
                p.next = curr;
                curr = prev.next;
            }
        }
        
        return fakehead.next;
    }
}