链表：奇偶重组

给定一个链表，把所有奇数节点放到偶数节点之前，奇节点和偶节点的相对位置不变。

public ListNode oddEvenList(ListNode head) {
    	if(head == null || head.next == null || head.next.next == null)
    		return head;
    	ListNode listOdd = new ListNode(0);
    	ListNode listEven = new ListNode(0);
    	ListNode currOdd = head;
    	ListNode currEven = head.next;
    	ListNode tailOdd = listOdd;
    	ListNode tailEven = listEven;
    	while(true){
    		tailOdd.next = currOdd;
    		tailEven.next = currEven;
    		tailOdd = currOdd;
    		tailEven = currEven;
            if(currOdd.next.next != null && currEven.next.next != null){
                currOdd = currOdd.next.next;
                currEven = currEven.next.next;
            }
            else if(currOdd.next.next != null){ //若链表要奇数个节点，需加上
                currOdd = currOdd.next.next;
                tailOdd.next = currOdd;
                tailOdd = currOdd;
                break;
            }
            else
                break;
    	}
    	tailOdd.next = listEven.next;
    	tailEven.next = null;
    	return listOdd.next;
    }