drink.cc.txt

Ulm大学2003-2004年竞赛题

// Problem   Drink
// Algorithm Simulation
// Runtime   O(1)
// Author    Walter Guttmann
// Date      24.01.2003

#include <cassert>
#include <fstream>
#include <iostream>

using namespace std;

ifstream in ("drink.in");

const double cw = 4.19;
const double ci = 2.09;
const double em = 335.0;

int main ()
{
  cout.setf(ios::fixed);
  cout.precision(1);
  while (1)
  {
    double mw, mi, tw, ti;
    in >> mw >> mi >> tw >> ti;
    if (mw == 0.0 && mi == 0.0 && tw == 0.0 && ti == 0.0)
      break;
    assert(mw >= 0.0 && mi >= 0.0 && mw + mi > 0.0);
    assert(0.0 <= tw && tw < 100.0 && -30.0 < ti && ti <= 0.0);

    double water0 = cw * mw * tw;
    double ice0 = ci * mi * (- ti);
    if (water0 <= ice0)
    {
      // cool water to zero
      ice0 -= water0;
      tw = 0.0;
      ti = (- ice0) / (ci * mi);
      // freeze some water
      water0 = em * mw;
      if (water0 <= ice0)
      {
        // freeze all water
        ice0 -= water0;
        ti = (- ice0) / (ci * mi);
        // mw now denotes ice of temperature 0
        // find equilibrium at temperature t where mi * t = mw * (tw - t)
        ti = mi * ti / (mi + mw);
        mi += mw;
        mw = 0.0;
      }
      else
      {
        // heat ice to zero
        ti = 0.0;
        mw -= ice0 / em;
        mi += ice0 / em;
      }
    }
    else
    {
      // heat ice to zero
      water0 -= ice0;
      tw = water0 / (cw * mw);
      ti = 0.0;
      // melt some ice
      ice0 = em * mi;
      if (water0 <= ice0)
      {
        // cool water to zero
        tw = 0.0;
        mw += water0 / em;
        mi -= water0 / em;
      }
      else
      {
        // melt all ice
        water0 -= ice0;
        tw = water0 / (cw * mw);
        // mi now denotes water of temperature 0
        // find equilibrium at temperature t where mi * t = mw * (tw - t)
        tw = mw * tw / (mw + mi);
        mw += mi;
        mi = 0.0;
      }
    }

    cout << mi << " g of ice and "
         << mw << " g of water at "
         << ti+tw << " C" << endl;
  }
  return 0;
}