wildlifemonitor.cpp

C++编程思想第二版第一册答案

//: C20:WildLifeMonitor.cpp
// From Thinking in C++, 2nd Edition
// Available at http://www.BruceEckel.com
// (c) Bruce Eckel 1999
// Copyright notice in Copyright.txt
#include <vector>
#include <map>
#include <string>
#include <algorithm>
#include <iostream>
#include <sstream>
#include <ctime>
using namespace std;

class DataPoint {
  int x, y; // Location coordinates
  time_t time; // Time of Sighting
public:
  DataPoint() : x(0), y(0), time(0) {}
  DataPoint(int xx, int yy, time_t tm) :
    x(xx), y(yy), time(tm) {}
  // Synthesized operator=, copy-constructor OK
  int getX() { return x; }
  int getY() { return y; }
  time_t* getTime() { return &time; }
};

string animal[] = { 
  "chipmunk", "beaver", "marmot", "weasel",
  "squirrel", "ptarmigan", "bear", "eagle",
  "hawk", "vole", "deer", "otter", "hummingbird",
};
const int asz = sizeof animal/sizeof *animal;
vector<string> animals(animal, animal + asz);

// All the information is contained in a 
// "Sighting," which can be sent to an ostream:
typedef pair<string, DataPoint> Sighting;

ostream& 
operator<<(ostream& os, const Sighting& s) {
  return os << s.first << " sighted at x= " << 
    s.second.getX() << ", y= " << s.second.getY()
    << ", time = " << ctime(s.second.getTime());
}

// A generator for Sightings:
class SightingGen {
  vector<string>& animals;
  static const int d = 100;
public:
  SightingGen(vector<string>& an) :
    animals(an) { srand(time(0)); }
  Sighting operator()() {
    Sighting result;
    int select = rand() % animals.size();
    result.first = animals[select];
    result.second = DataPoint(
      rand() % d, rand() % d, time(0));
    return result;
  }
};

typedef multimap<string, DataPoint> DataMap;
typedef DataMap::iterator DMIter;

int main() {
  DataMap sightings;
  generate_n(
    inserter(sightings, sightings.begin()),
    50, SightingGen(animals));
  // Print everything:
  copy(sightings.begin(), sightings.end(),
    ostream_iterator<Sighting>(cout, ""));
  // Print sightings for selected animal:
  while(true) {
    cout << "select an animal or 'q' to quit: ";
    for(int i = 0; i < animals.size(); i++)
      cout <<'['<< i <<']'<< animals[i] << ' ';
    cout << endl;
    string reply;
    cin >> reply;
    if(reply.at(0) == 'q') return 0;
    istringstream r(reply);
    int i;
    r >> i; // Converts to int
    i %= animals.size();
    // Iterators in "range" denote begin, one 
    // past end of matching range:
    pair<DMIter, DMIter> range = 
      sightings.equal_range(animals[i]);
    copy(range.first, range.second,
      ostream_iterator<Sighting>(cout, ""));
  }
} ///:~