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86. Partition List

时间:2016-10-12 16:58:46      阅读:151      评论:0      收藏:0      [点我收藏+]

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Given a linked list and a value x, partition it such that all nodes less than x come before nodes greater than or equal to x.

You should preserve the original relative order of the nodes in each of the two partitions.

For example,
Given 1->4->3->2->5->2 and x = 3,
return 1->2->2->4->3->5.

思路:把list分成两份,一份是比pivot小,一份是比pivot大,然后连接起来。用dummy node来partition list,因为head大小无法判断。注意最后要把快的list尾巴断开,用null来断,不然可能还连接着其他node。

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) { val = x; }
 * }
 */
public class Solution {
    public ListNode partition(ListNode head, int x) {
    if(head==null||head.next==null)return head;
    ListNode dummy1=new ListNode(-1);
    ListNode dummy2=new ListNode(-1);
    ListNode copydummy1=dummy1;
    ListNode copydummy2=dummy2;
    while(head!=null){
        if(head.val<x){
            copydummy1.next=head;
            copydummy1=copydummy1.next;
        }else{
            copydummy2.next=head;
            copydummy2=copydummy2.next;
        }
        head=head.next;
    }
    copydummy2.next=null;
    copydummy1.next=dummy2.next;
    return dummy1.next;
    }
}

 

86. Partition List

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原文地址:http://www.cnblogs.com/Machelsky/p/5953215.html

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