题解 | #链表中环的入口结点#

/**
 * struct ListNode {
 *	int val;
 *	struct ListNode *next;
 * };
 */
/**
 * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
 *
 * 
 * @param pHead ListNode类 
 * @return ListNode类
 */
struct ListNode* EntryNodeOfLoop(struct ListNode* pHead ) {
    // write code here
    struct ListNode *curr = pHead;

    if (!pHead)
        return NULL;
    while(curr) {
        if (curr->val >> 20 & 0x1) {
            curr->val &= ~(1 << 20);
            break;
        }
        curr->val |= 1 << 20;
        curr = curr->next;
    }
    return curr;
}