Minimum Speed to Arrive on Time LeetCode solution in C++

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class Solution {
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  bool canReachInTime(const vector<int> &dist, const double hour, int speed) {
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    double time = 0;
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    for (int i = 0; i < dist.size() - 1; ++i) time += ((dist[i] + speed - 1) / speed);
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    time += ((double)dist.back()) / speed;
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    return time <= hour;
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  }
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 public:
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  int minSpeedOnTime(vector<int> &dist, double hour) {
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    int N = dist.size();
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    if (hour <= (double)(N - 1)) return -1;
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    int lo = 1, hi = 1e7, mi;
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    while (lo < hi) {
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      mi = (lo + hi) / 2;
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      if (canReachInTime(dist, hour, mi))
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        hi = mi;
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      else
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        lo = mi + 1;
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    }
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    return hi;
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  }
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};