Find Three Consecutive Integers That Sum to a Given Number LeetCode solution in C++

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class Solution {
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 public:
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  vector<long long> sumOfThree(long long num) {
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    // binary Search
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    long long lo = -1; // -1 becoz we have num == 0 as well if we put lo=0 then
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                       // it will fail in 1 testcase
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    long long hi = num;
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    while (lo <= hi) {
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      long long mid = lo + (hi - lo) / 2;
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      long long val = 3 * mid + 3; // mid+mid+1mid+2 == num
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      if (val == num) {
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        return {mid, mid + 1, mid + 2};
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      } else if (val > num) {
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        hi = mid - 1;
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      } else {
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        lo = mid + 1;
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      }
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    }
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    return {};
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  }
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};