Guess Number Higher or Lower LeetCode solution in C++

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class Solution {
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 public:
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  int guessNumber(int n) {
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    int s = 1, e = n;
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    int mid = s + (e - s) / 2;
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    while (s <= e) {
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      if (guess(mid) == 0) {
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        return mid;
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      }
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      else if (guess(mid) == -1) {
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        e = mid - 1;
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      }
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      else if (guess(mid) == 1) {
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        s = mid + 1;
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      }
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      mid = s + (e - s) / 2;
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    }
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    return mid;
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  }
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};