Set sorted output

gen.py

import random

n = 20000000
v = 100000000
l = list(range(v))
random.shuffle(l)
l = l[:n]

with open('input.txt', 'w') as f:
    print('\n'.join((str(x) for x in l)), file=f)

with open('answer.txt', 'w') as f:
    print('\n'.join((str(x) for x in sorted(l))), file=f)

test.cpp

#include <bitset>
#include <fstream>

const int N = 1e8;

std::bitset<N> s;

int main() {
    std::ifstream input("input.txt");
    std::ofstream output("output.txt");

    int x;
    while (input >> x) s.set(x);
    for (int i = 0; i < N; i++)
        if (s[i]) output << i << "\n";
}