Task: Primes - allocate descendants to their ancestors


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

typedef unsigned long long integer;


std::vector<integer> get_ancestors(const std::vector<integer>& ancestor, integer n) {
    std::vector<integer> result;
    for (integer a = ancestor[n]; a != 0 && a != n; ) {
        n = a;
        a = ancestor[n];
        result.push_back(n);
    }
    return result;
}

void print_vector(const std::vector<integer>& vec) {
    if (vec.empty()) {
        std::cout << "none\n";
        return;
    }
    auto i = vec.begin();
    std::cout << *i++;
    for (; i != vec.end(); ++i)
        std::cout << ", " << *i;
    std::cout << '\n';
}

bool is_prime(integer n) {
    if (n < 2)
        return false;
    if (n % 2 == 0)
        return n == 2;
    for (integer p = 3; p * p <= n; p += 2) {
        if (n % p == 0)
            return false;
    }
    return true;
}

int main(int argc, char** argv) {
    const size_t limit = 100;

    std::vector<integer> ancestor(limit, 0);
    std::vector<std::vector<integer>> descendants(limit);

    for (size_t prime = 0; prime < limit; ++prime) {
        if (!is_prime(prime))
            continue;
        descendants[prime].push_back(prime);
        for (size_t i = 0; i + prime < limit; ++i) {
            integer s = i + prime;
            for (integer n : descendants[i]) {
                integer prod = n * prime;
                descendants[s].push_back(prod);
                if (prod < limit)
                    ancestor[prod] = s;
            }
        }
    }

    
    size_t total_descendants = 0;
    for (integer i = 1; i < limit; ++i) {
        std::vector<integer> ancestors(get_ancestors(ancestor, i));
        std::cout << "[" << i << "] Level: " << ancestors.size() << '\n';
        std::cout << "Ancestors: ";
        std::sort(ancestors.begin(), ancestors.end());
        print_vector(ancestors);
        
        std::cout << "Descendants: ";
        std::vector<integer>& desc = descendants[i];
        if (!desc.empty()) {
            std::sort(desc.begin(), desc.end());
            if (desc[0] == i)
                desc.erase(desc.begin());
        }
        std::cout << desc.size() << '\n';
        total_descendants += desc.size();
        if (!desc.empty())
            print_vector(desc);
        std::cout << '\n';
    }
    std::cout << "Total descendants: " << total_descendants << '\n';
    return 0;
}



Go: package main

import (
    "fmt"
    "sort"
)

func getPrimes(max int) []int {
    if max < 2 {
        return []int{}
    }
    lprimes := []int{2}
outer:
    for x := 3; x <= max; x += 2 {
        for _, p := range lprimes {
            if x%p == 0 {
                continue outer
            }
        }
        lprimes = append(lprimes, x)
    }
    return lprimes
}

func main() {
    const maxSum = 99
    descendants := make([][]int64, maxSum+1)
    ancestors := make([][]int, maxSum+1)
    for i := 0; i <= maxSum; i++ {
        descendants[i] = []int64{}
        ancestors[i] = []int{}
    }
    primes := getPrimes(maxSum)

    for _, p := range primes {
        descendants[p] = append(descendants[p], int64(p))
        for s := 1; s < len(descendants)-p; s++ {
            temp := make([]int64, len(descendants[s]))
            for i := 0; i < len(descendants[s]); i++ {
                temp[i] = int64(p) * descendants[s][i]
            }
            descendants[s+p] = append(descendants[s+p], temp...)
        }
    }

    for _, p := range append(primes, 4) {
        le := len(descendants[p])
        if le == 0 {
            continue
        }
        descendants[p][le-1] = 0
        descendants[p] = descendants[p][:le-1]
    }
    total := 0

    for s := 1; s <= maxSum; s++ {
        x := descendants[s]
        sort.Slice(x, func(i, j int) bool {
            return x[i] < x[j]
        })
        total += len(descendants[s])
        index := 0
        for ; index < len(descendants[s]); index++ {
            if descendants[s][index] > int64(maxSum) {
                break
            }
        }
        for _, d := range descendants[s][:index] {
            ancestors[d] = append(ancestors[s], s)
        }
        if (s >= 21 && s <= 45) || (s >= 47 && s <= 73) || (s >= 75 && s < maxSum) {
            continue
        }
        temp := fmt.Sprintf("%v", ancestors[s])
        fmt.Printf("%2d: %d Ancestor(s): %-14s", s, len(ancestors[s]), temp)
        le := len(descendants[s])
        if le <= 10 {
            fmt.Printf("%5d Descendant(s): %v\n", le, descendants[s])
        } else {
            fmt.Printf("%5d Descendant(s): %v\b ...]\n", le, descendants[s][:10])
        }
    }
    fmt.Println("\nTotal descendants", total)
}