Determine whether there is a ring on the linked list and return to the start position of the ring entry
Title link
**Thoughts: **First use the fast and slow pointer to judgeLink ListWhether there is a ring, if there is a ring, that is, fast==slow. Take the current slow pointer as the starting point and walk again. When you meet next time, return to slow. If the linked list does not have a ring, return null.
The wonderful uses of fast and slow pointers:
Fast and slow pointers are mainly used to solve linked list problems. Among the fast and slow pointers, because after each move, the fast pointer will walk one more node than the slow pointer, so after entering the ring-shaped link list, no matter how many nodes are separated, the slow pointer will always be caught up by the fast pointer and overlap. At this time, it can be judged that there must be a ring.
Code display:
Title link
**Thoughts: **First use the fast and slow pointer to judgeLink ListWhether there is a ring, if there is a ring, that is, fast==slow. Take the current slow pointer as the starting point and walk again. When you meet next time, return to slow. If the linked list does not have a ring, return null.
The wonderful uses of fast and slow pointers:
Fast and slow pointers are mainly used to solve linked list problems. Among the fast and slow pointers, because after each move, the fast pointer will walk one more node than the slow pointer, so after entering the ring-shaped link list, no matter how many nodes are separated, the slow pointer will always be caught up by the fast pointer and overlap. At this time, it can be judged that there must be a ring.
Code display: