字符串翻转

代码能力，for循环

class Solution {
public:
    ListNode* ReverseList(ListNode* pHead) {
        if(pHead == NULL || pHead->next == NULL){
            return pHead;}
        ListNode *p=NULL;
        for(p;pHead;swap(p,pHead)){
         swap(pHead->next,p);
        }
        return p;
    }
};