题目：

题解：

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