Композиция числа

#include <algorithm>
#include <iostream>
#include <string>
#include <vector>
using namespace std;
class Composition {
public:
    Composition(int number) : number(number) {
        box.emplace_back(to_string(number));
    }
    vector<string> result() {
        Compare comp;
        run();
        sort(box.begin(), box.end(), comp);
        return box;
    }
private:
    int number;
    char buffer[0xFFFF];
    vector<string> box;
    struct Compare {
        bool operator()(const string& a, const string& b) {
            return a.length() < b.length();
        }
    };
    void decomposition(int num, int beg, int pos) {
        int end = strlen(buffer);
        _itoa_s(num, buffer + pos, sizeof(int), 10);
        int next, limit;
        buffer[end] = 0;
        box.push_back(string(buffer));
        for (next = beg, limit = (num >> 1); next <= limit; ++next) {
            _itoa_s(next, buffer + pos, sizeof(int), 10);
            end = strlen(buffer);
            buffer[end] = ' ';
            decomposition(num - next, next, end + 1);
        }
    }
    void run() {
        int next, limit, length;
        for (next = 1, limit = (number >> 1); next <= limit; ++next) {
            _itoa_s(next, buffer, sizeof(int), 10);
            length = strlen(buffer);
            buffer[length] = ' ';
            decomposition(number - next, next, length + 1);
        }
    }
};
int main() {
    int n = 10;
    Composition сomposition(n);
    auto result = сomposition.result();
    auto x = 0;
    for (const auto& item : result) {
        cout << ++x << ") " << item << '\n';
    }
    system("pause > nul");
}