Invitation to Hunt The Code

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vortex_nitt's blog

Invitation to Hunt The Code

By vortex_nitt, history, 4 years ago, In English

Given a problem, you can think of a solution. But given an answer, can you think of a solution? Vortex welcomes you to participate in a one of a kind event with Hunt the Code! Twist your brain to generate solutions for a given answer!

Contest Link : https://www.hackerrank.com/hunt-the-code-2022

Contest Timing : 20:00 to 22:30 IST, 26th Feb

Duration : 2:30 hours

CASH PRIZES Distribution (Only for Indians):

INR 1500
INR 1000
INR 500

Registeration for Prizes: Either fill up the GForm or use the same email registered with Vortex website to participate in this event for validation to get the prizes

For more info : Hunt The Code

We have put great effort into preparing for this contest. We genuinely hope that you will enjoy retracing the source code from the combination of inputs & outputs and writing optimised code to run it against hidden test cases.

Good Luck & Have Fun! Hope to see you participating!!

reverse coding

vortex_nitt
4 years ago
10

Comments (8)

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anujdhillxn

4 years ago, hide # |

← Rev. 2 →

Why is this submission giving WA for Q9? I checked it for so many samples and it was right everytime. On submission it was showing WA for all the test cases. Basically just multiply the answer with $$$i$$$ if $$$i$$$ is a prime, else increment i :(

Code

#include <bits/stdc++.h>
// #include <ext/pb_ds/assoc_container.hpp>
// #include <ext/pb_ds/tree_policy.hpp>

// using namespace __gnu_pbds;
using namespace std;

template <class X, class Y>
ostream &operator<<(ostream &os, pair<X, Y> const &p)
{
    return os << "(" << p.first << ", " << p.second << ") ";
}
template <class Ch, class Tr, class Container>
basic_ostream<Ch, Tr> &operator<<(basic_ostream<Ch, Tr> &os, Container const &x)
{
    os << "[ ";
    for (auto &y : x)
        os << y << ", ";
    return os << "]\n";
}
#define int long long
#define len(a) (int)a.size()
#define ordered_set(T) tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>
const long long INF = 1e18;
const double EPS = 1e-9;
const int di[8] = {1, 0, -1, 0, 1, -1, -1, 1};
const int dj[8] = {0, 1, 0, -1, 1, 1, -1, -1};
// dp?, graph?, bs on answer?, compress/sort queries?, stupid observation?


int32_t main()
{
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    int M = 1e9 + 7;
    int n;
    cin>>n;
    vector<int> spf(n+1);
    for (int i = 1; i <= n; i++)
        spf[i] = i;
    for (int i = 2; i <= n; i++)
    {
        if (spf[i] == i)
        {
            //primes.push_back(i);
            for (long long j = (long long)i * i; j <= n; j += i)
            {
                if (spf[j] == j)
                    spf[j] = i;
            }
        }
    }
    long long p = 1;
    for(int i=2;i<=n;i++){
        if(spf[i] == i) p= (p*i)%M;
    }
    cout<<p<<'\n';
    return 0;
}

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master._.mind

4 years ago, hide # ^ |

← Rev. 3 →

Your idea to multiply all primes $$$ \lt = n$$$ is correct. You just had to use int instead of long long and let the product overflow, to get full points. Idk if that was intended, but that gave me full points. I thought about this after seeing the output for $$$21 - 40$$$. Notice the using ll = int;

My code

#ifdef LOCAL
#include "Akshat.hpp"
#else
#include "bits/stdc++.h"
using namespace std;
#define dbg(...)
#endif
using ll = int;
// using ll = long long;
auto sz = [](const auto &container) -> ll { return ll(container.size()); };
#define all(x) (x).begin(), (x).end()
const ll MOD = 1e9 + 7;
// const ll INF = 1e18;

const ll N = 10000000;
array<ll, N + 1> spf;
vector<ll> pr;
void fill() {
    for (ll i = 2; i <= N; ++i) {
        if (spf[i] == 0) spf[i] = i, pr.push_back(i);
        for (ll j = 0; j < (ll)pr.size() && pr[j] <= spf[i] && i * pr[j] <= N; ++j)
            spf[i * pr[j]] = pr[j];
    }
}

bool isPrime(ll n) {
    assert(n >= 0 && n <= N);
    return (spf[n] == n);
}

void Solution() {
    ll n;
    cin >> n;
    ll P = 1;
    for (ll i = 0; i < sz(pr) && pr[i] <= n; ++i) {
        P *= pr[i];
        P %= MOD;
    }
    cout << P % MOD << '\n';
}

int main() {
    fill();
    cin.tie(nullptr)->sync_with_stdio(false);
#ifdef LOCAL
    [[maybe_unused]] FILE *in = freopen("input.txt", "r", stdin);
    [[maybe_unused]] FILE *out = freopen("output.txt", "w", stdout);
#endif
    cout << fixed << setprecision(12);
    int tc = 1;
    // cin >> tc;
    while (tc--) {
        Solution();
    }
    return 0;
}

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