coding interviews 15 反转链表

public ListNode ReverseList(ListNode head) {
	//this is an operation between three node
	ListNode p = head;
	ListNode next =null;
	ListNode pre = null;
	
	if(p != null){
 	while(p.next!=null){
 		//1. split between p and p.next
 		next = p.next;
 		p.next = null;
 		//2. reverse 
 		p.next = pre;
 		//3. change position
 		pre = p;
 		p = next;
 	}
 	
 	p.next = pre;
    	
	}

	return p;
}