题目：

题解：

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