stackoverflow - cities and states

citites.cc

#include <iostream>
#include <string>
#include <vector>
#include <map>
#include <algorithm>
#include <limits>

using std::string;
using std::vector;
using std::map;
using std::pair;
using std::istream;

struct CityEntry {
  string name;
  string state;
  unsigned int inhabitants;
};

struct StateInhabitants {
  unsigned int total;
  unsigned int lowest;
  // lowest needs to be set to the maximum value, otherwise you'd need a
  // special case during the iteration.
  StateInhabitants()
    : total(0), lowest(std::numeric_limits<unsigned int>::max())
  {}
};

vector<CityEntry> read_cities(istream & input) {
  vector<CityEntry> entries;
  string name;
  string state;
  unsigned int inhabitants;
  while (input >> name >> state >> inhabitants) {
    entries.push_back(CityEntry{name, state, inhabitants});
  }
  return entries;
}

int main(int, char **) {
  // Input phase
  vector<CityEntry> cities = read_cities(std::cin);
  // Transform input to wanted representation
  map<string, StateInhabitants> state_info;
  for (CityEntry const & city : cities) {
    StateInhabitants & inhabitants = state_info[city.state];
    inhabitants.total += city.inhabitants;
    inhabitants.lowest = std::min(inhabitants.lowest, city.inhabitants);
  }
  // Print results
  for (pair<string, StateInhabitants> info : state_info) {
    std::cout
      << info.first
      << " " << info.second.lowest
      << " " << info.second.total
      << std::endl;
  }
  return 0;
}