Task: Sum and product puzzle


C++: #include <algorithm>
#include <iostream>
#include <map>
#include <vector>

std::ostream &operator<<(std::ostream &os, std::vector<std::pair<int, int>> &v) {
    for (auto &p : v) {
        auto sum = p.first + p.second;
        auto prod = p.first * p.second;
        os << '[' << p.first << ", " << p.second << "] S=" << sum << " P=" << prod;
    }
    return os << '\n';
}

void print_count(const std::vector<std::pair<int, int>> &candidates) {
    auto c = candidates.size();
    if (c == 0) {
        std::cout << "no candidates\n";
    } else if (c == 1) {
        std::cout << "one candidate\n";
    } else {
        std::cout << c << " candidates\n";
    }
}

auto setup() {
    std::vector<std::pair<int, int>> candidates;

    
    for (int x = 2; x <= 98; x++) {
        
        for (int y = x + 1; y <= 98; y++) {
            if (x + y <= 100) {
                candidates.push_back(std::make_pair(x, y));
            }
        }
    }

    return candidates;
}

void remove_by_sum(std::vector<std::pair<int, int>> &candidates, const int sum) {
    candidates.erase(std::remove_if(
        candidates.begin(), candidates.end(),
        [sum](const std::pair<int, int> &pair) {
            auto s = pair.first + pair.second;
            return s == sum;
        }
    ), candidates.end());
}

void remove_by_prod(std::vector<std::pair<int, int>> &candidates, const int prod) {
    candidates.erase(std::remove_if(
        candidates.begin(), candidates.end(),
        [prod](const std::pair<int, int> &pair) {
            auto p = pair.first * pair.second;
            return p == prod;
        }
    ), candidates.end());
}

void statement1(std::vector<std::pair<int, int>> &candidates) {
    std::map<int, int> uniqueMap;

    std::for_each(
        candidates.cbegin(), candidates.cend(),
        [&uniqueMap](const std::pair<int, int> &pair) {
            auto prod = pair.first * pair.second;
            uniqueMap[prod]++;
        }
    );

    bool loop;
    do {
        loop = false;
        for (auto &pair : candidates) {
            auto prod = pair.first * pair.second;
            if (uniqueMap[prod] == 1) {
                auto sum = pair.first + pair.second;
                remove_by_sum(candidates, sum);

                loop = true;
                break;
            }
        }
    } while (loop);
}

void statement2(std::vector<std::pair<int, int>> &candidates) {
    std::map<int, int> uniqueMap;

    std::for_each(
        candidates.cbegin(), candidates.cend(),
        [&uniqueMap](const std::pair<int, int> &pair) {
            auto prod = pair.first * pair.second;
            uniqueMap[prod]++;
        }
    );

    bool loop;
    do {
        loop = false;
        for (auto &pair : candidates) {
            auto prod = pair.first * pair.second;
            if (uniqueMap[prod] > 1) {
                remove_by_prod(candidates, prod);

                loop = true;
                break;
            }
        }
    } while (loop);
}

void statement3(std::vector<std::pair<int, int>> &candidates) {
    std::map<int, int> uniqueMap;

    std::for_each(
        candidates.cbegin(), candidates.cend(),
        [&uniqueMap](const std::pair<int, int> &pair) {
            auto sum = pair.first + pair.second;
            uniqueMap[sum]++;
        }
    );

    bool loop;
    do {
        loop = false;
        for (auto &pair : candidates) {
            auto sum = pair.first + pair.second;
            if (uniqueMap[sum] > 1) {
                remove_by_sum(candidates, sum);

                loop = true;
                break;
            }
        }
    } while (loop);
}

int main() {
    auto candidates = setup();
    print_count(candidates);

    statement1(candidates);
    print_count(candidates);

    statement2(candidates);
    print_count(candidates);

    statement3(candidates);
    print_count(candidates);

    std::cout << candidates;

    return 0;
}


C#: using System;
using System.Linq;
using System.Collections.Generic;

public class Program
{
    public static void Main()
    {
        const int maxSum = 100;
        var pairs = (
            from X in 2.To(maxSum / 2 - 1)
            from Y in (X + 1).To(maxSum - 2).TakeWhile(y => X + y <= maxSum)
            select new { X, Y, S = X + Y, P = X * Y }
            ).ToHashSet();

        Console.WriteLine(pairs.Count);
        
        var uniqueP = pairs.GroupBy(pair => pair.P).Where(g => g.Count() == 1).Select(g => g.Key).ToHashSet();
        
        pairs.ExceptWith(pairs.GroupBy(pair => pair.S).Where(g => g.Any(pair => uniqueP.Contains(pair.P))).SelectMany(g => g));
        Console.WriteLine(pairs.Count);
        
        pairs.ExceptWith(pairs.GroupBy(pair => pair.P).Where(g => g.Count() > 1).SelectMany(g => g));
        Console.WriteLine(pairs.Count);
        
        pairs.ExceptWith(pairs.GroupBy(pair => pair.S).Where(g => g.Count() > 1).SelectMany(g => g));
        Console.WriteLine(pairs.Count);
        
        foreach (var pair in pairs) Console.WriteLine(pair);
    }
}

public static class Extensions
{
    public static IEnumerable<int> To(this int start, int end) {
        for (int i = start; i <= end; i++) yield return i;
    }
    
    public static HashSet<T> ToHashSet<T>(this IEnumerable<T> source) => new HashSet<T>(source);
}