基于链表的快速排序及归并排序

归并排序

package 算法和数据结构;
/**
* Filename : LinkedList_MergeSort.java
* Author : [email protected]
* Creation time : 下午5:47:02 - 2017年3月26日
* Description :
*/

class ListNode {
    int val;
    ListNode next;
    ListNode(int x){
        val = x;
        next = null;
    }
}
public class LinkedList_MergeSort{
    public ListNode sortList(ListNode head){
        if(head==null||head.next==null){
            return head;
        }
        ListNode mid=findMid(head);
        ListNode right=mid.next;
        mid.next=null;
        return merge(sortList(head),sortList(right));
    }
    private ListNode merge(ListNode head1,ListNode head2){
        ListNode dummy=new ListNode(0);
        ListNode cur=dummy;
        while(head1!=null&&head2!=null){
            if(head1.val<=head2.val){
                cur.next=head1;
                head1=head1.next;
            }else{
                cur.next=head2;
                head2=head2.next;
            }
            cur=cur.next;
        }
        if(head1!=null){
            cur.next=head1;
        }else if(head2!=null){
            cur.next=head2;
        }
        return dummy.next;
    }
    private ListNode findMid(ListNode head){
        if(head==null){
            return head;
        }
        ListNode slow=head;
        ListNode fast=head;
        while(fast.next!=null&&fast.next.next!=null){
            fast=fast.next.next;
            slow=slow.next;
        }
        return slow;
    }
}

快速排序

package 算法和数据结构;
/**
* Filename : LinkedList_QuickSort.java
* Author : [email protected]
* Creation time : 下午5:50:18 - 2017年3月26日
* Description :
*/

public class LinkedList_QuickSort{
    public ListNode sortList(ListNode head){
        return quickSort(head,null);
    }
    private ListNode quickSort(ListNode head,ListNode end){
        if(head!=end){
            ListNode cur=partion(head,end);
            quickSort(head,cur);
            quickSort(cur.next,end);
        }
        return head;
    }
    private ListNode partion(ListNode head,ListNode end){
        int key=head.val;
        ListNode p=head;
        ListNode q=head.next;
        while(q!=end){
            if(q.val<key){
                p=p.next;
                swap(p,q);
            }
            q=q.next;
        }
        swap(head,p);
        return p;
    }
    private void swap(ListNode p,ListNode q){
        int temp=p.val;
        p.val=q.val;
        q.val=temp;
    }
}