SRM467 Div1 Easy

250
こういう類の問題は不得手だわー。厳しかった。

class LateProfessor {
public:
  double getProbability(int waitTime, int walkTime, int lateTime, int bestArrival, int worstArrival) {

    const int cy = waitTime + walkTime;

    if (bestArrival == worstArrival) {
      int t = bestArrival % cy;
      if (waitTime < t) return t <= cy - lateTime;
      return 0;
    }

    double ret = 0;

    for (int t = bestArrival; t < worstArrival; ++t) {
      int u = t % cy;
      if (cy <= u + lateTime) continue;        
      if (u < waitTime) continue;
      ++ret;
    }

    return ret / (double)(worstArrival - bestArrival);
  }

};