Informatikos VBE 2013, 2 užduotis

#include <iostream>
#include <fstream>
#include <string>
#include <algorithm>

using namespace std;

int total_cities = 0,
    total_regions = 0;

struct City {
    string name;
    string region;
    int population;
} cities[103];

struct Region {
    string name = "";
    int population = 0;
    int smallest_population = 600000; // 600 000 is highest possible value
} regions[10];

void read_data();
void write_data();
void add_region_city(int index, int population);
bool region_compare(Region region1, Region region2);

int main()
{
    read_data();

    for (int i = 0; i < total_cities; i++) {

        for (int r = 0; r < 10; r++) {
            // if region name is already in list, skip loop
            if (regions[r].name == cities[i].region) {
                add_region_city(r, cities[i].population);
                break;
            }

            // if region's name isn't set and current index is free, set region name
            if (regions[r].name == "") {
                total_regions++;
                regions[r].name = cities[i].region;
                add_region_city(r, cities[i].population);
                break;
            }
        }

    }

    sort(regions, regions + total_regions, region_compare);

    write_data();
    return 0;
}

/**
 * Reads data from input file
 */
void read_data() {
    ifstream datafile;
    datafile.open("U2.txt");

    if (datafile.is_open()) {
        datafile >> total_cities;

        for (int i = 0; i < total_cities; i++) {
            datafile >> cities[i].name >> cities[i].region >> cities[i].population;
        }
    }
}

/**
 * Writes results to output file
 */
void write_data() {
    ofstream outputfile;
    outputfile.open("U2Rez.txt");

    if (outputfile.is_open()) {
        outputfile << total_regions << endl;
        for (int i = 0; i < total_regions; i++) {
            outputfile << regions[i].name << " ";
            outputfile << regions[i].smallest_population << " ";
            outputfile << regions[i].population << " ";
            outputfile << endl;
        }
    }
}

/**
  * Adds city population to region population, and checks,
  * if it's smallest city population
  *
  * int index - array index of region
  * int population - population of city
  */
void add_region_city(int index, int population) {
    regions[index].population += population;

    if (regions[index].smallest_population > population)
        regions[index].smallest_population = population;
}

/**
  * Comparing function for sorting regions by smallest city
  * and alphabet (sort function's third argument)
  */
bool region_compare(Region region1, Region region2) {
    if (region1.smallest_population == region2.smallest_population) {
        return region1.name < region2.name;
    } else {
        return region1.smallest_population < region2.smallest_population;
    }
}