题解 | #链表中环的入口结点#

空间复杂度O(1),时间复杂度估计略大于o(n),不需额外数组或指针

/*
struct ListNode {
    int val;
    struct ListNode *next;
    ListNode(int x) :
        val(x), next(NULL) {
    }
};
*/
class Solution {
public:
    ListNode* EntryNodeOfLoop(ListNode* pHead) {
        while(pHead){
            if(pHead->val <= -100000){
                // do something
                while(pHead->val <= -10000){
                    pHead->val+=100000;
                    pHead = pHead->next;
                }
                return pHead;
            }
            pHead->val -= 1000000;
            pHead = pHead->next;
        }
        return NULL;
    }
};