Circular Array Loop LeetCode solution in C++

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class Solution {
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 public:
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  int next(vector<int> &nums, int i) {
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    int n = nums.size();
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    return (n + nums[i] + i) % n;
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  }
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  bool circularArrayLoop(vector<int> &nums) {
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    int n = nums.size();
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    // we can use slow and fast pointer to check whether there is loop or not
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    for (int &num : nums) num %= n;
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    for (int i = 0; i < n; i++) {
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      int slow = i, fast = i;
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      while (nums[slow] * nums[next(nums, fast)] > 0 &&
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             nums[slow] * nums[next(nums, next(nums, fast))] > 0) {
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        slow = next(nums, slow);
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        fast = next(nums, next(nums, fast));
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        if (slow == fast) {
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          if (slow == next(nums, slow)) // single length
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            return false;
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          return true;
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        }
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      }
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      /// DONOT TRAVERSE WHERE THERE IS NO PATH TO GET LOOP.
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      int j = i;
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      int val = nums[i];
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      while (nums[j] * val > 0) {
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        int nexx = next(nums, j);
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        nums[j] = 0;
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        j = nexx;
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      }
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    }
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    return false;
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  }
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};