题目：

题解：

class Solution {public boolean circularArrayLoop(int[] nums) {int n = nums.length;for (int i = 0; i < n; i++) {if (nums[i] == 0) {continue;}int slow = i, fast = next(nums, i);// 判断非零且方向相同while (nums[slow] * nums[fast] > 0 && nums[slow] * nums[next(nums, fast)] > 0) {if (slow == fast) {if (slow != next(nums, slow)) {return true;} else {break;}}slow = next(nums, slow);fast = next(nums, next(nums, fast));}int add = i;while (nums[add] * nums[next(nums, add)] > 0) {int tmp = add;add = next(nums, add);nums[tmp] = 0;}}return false;}public int next(int[] nums, int cur) {int n = nums.length;return ((cur + nums[cur]) % n + n) % n; // 保证返回值在 [0,n) 中}
}