题目：

题解：

func circularArrayLoop(nums []int) bool {n := len(nums)next := func(cur int) int {return ((cur+nums[cur])%n + n) % n // 保证返回值在 [0,n) 中}for i, num := range nums {if num == 0 {continue}slow, fast := i, next(i)// 判断非零且方向相同for nums[slow]*nums[fast] > 0 && nums[slow]*nums[next(fast)] > 0 {if slow == fast {if slow == next(slow) {break}return true}slow = next(slow)fast = next(next(fast))}add := ifor nums[add]*nums[next(add)] > 0 {tmp := addadd = next(add)nums[tmp] = 0}}return false
}