Submission #546214

#	Time	Username	Problem	Language	Result	Execution time	Memory
546214		SmolBrain	Bootfall (IZhO17_bootfall)	C++17	100 / 100	725 ms	33268 KiB

bootfall

// Om Namah Shivaya
// GM in 119 days

#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace std;
using namespace __gnu_pbds;

template <class T> using Tree = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;

typedef long long int ll;
typedef long double ld;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;

#define fastio ios_base::sync_with_stdio(false); cin.tie(NULL)
#define endl '\n'
#define pb push_back
#define conts continue
#define all(a) a.begin(), a.end()
#define rall(a) a.rbegin(), a.rend()
#define yes cout << "YES" << endl
#define no cout << "NO" << endl
#define ff first
#define ss second
#define ceil2(x,y) ((x+y-1) / (y))
#define sz(a) a.size()
#define setbits(x) __builtin_popcountll(x)
#ifndef ONLINE_JUDGE
#define debug(x) cout << #x <<" = "; print(x); cout << endl
#else
#define debug(x)
#endif

#define rep(i,n) for(int i = 0; i < n; ++i)
#define rep1(i,n) for(int i = 1; i <= n; ++i)
#define rev(i,s,e) for(int i = s; i >= e; --i)
#define trav(i,a) for(auto &i : a)

bool iseven(ll n) {if ((n & 1) == 0) return true; return false;}

void print(ll t) {cout << t;}
void print(int t) {cout << t;}
void print(string t) {cout << t;}
void print(char t) {cout << t;}
void print(double t) {cout << t;}
void print(ld t) {cout << t;}

template <class T, class V> void print(pair <T, V> p);
template <class T> void print(vector <T> v);
template <class T> void print(set <T> v);
template <class T, class V> void print(map <T, V> v);
template <class T> void print(multiset <T> v);
template <class T, class V> void print(pair <T, V> p) {cout << "{"; print(p.ff); cout << ","; print(p.ss); cout << "}";}
template <class T> void print(vector <T> v) {cout << "[ "; for (T i : v) {print(i); cout << " ";} cout << "]";}
template <class T> void print(set <T> v) {cout << "[ "; for (T i : v) {print(i); cout << " ";} cout << "]";}
template <class T> void print(multiset <T> v) {cout << "[ "; for (T i : v) {print(i); cout << " ";} cout << "]";}
template <class T, class V> void print(map <T, V> v) {cout << "[ "; for (auto i : v) {print(i); cout << " ";} cout << "]";}
template<typename T> void amin(T &a, T b) { a = min(a, b); }
template<typename T> void amax(T &a, T b) { a = max(a, b); }

void usaco(string filename) {
    freopen((filename + ".in").c_str(), "r", stdin);
    freopen((filename + ".out").c_str(), "w", stdout);
}

const int MOD = 1e9 + 7;
const int maxn = 500 * 500 + 1;
const int inf1 = 1e9 + 5;
const ll inf2 = ll(1e18) + 5;

void solve(int test_case)
{
    // thanks to the 1st sol here (Mr.Francois Vogel's sol) for providing me the sol intuition: https://usaco.guide/problem-solutions/
    int n; cin >> n;
    vector<int> a(n);
    rep(i, n) cin >> a[i];

    bitset<maxn> pref[n], suff[n];
    bitset<maxn> b;
    b[0] = 1;

    rep(i, n) {
        b |= (b << a[i]);
        pref[i] = b;
    }

    b = bitset<maxn>(0);
    b[0] = 1;

    rev(i, n - 1, 0) {
        b |= (b << a[i]);
        suff[i] = b;
    }

    int sum = accumulate(all(a), 0);

    if (sum & 1) {
        cout << 0 << endl;
        return;
    }

    if (b[sum / 2] == 0) {
        cout << 0 << endl;
        return;
    }

    vector<int> cnt(maxn);

    rep(i, n) {
        bitset<maxn> curr;

        if (i < n / 2) {
            curr = suff[i + 1];
            rep(j, i) curr |= (curr << a[j]);
        }
        else {
            curr = pref[i - 1];
            for (int j = i + 1; j < n; ++j) curr |= (curr << a[j]);
        }

        sum = 0;

        rep(j, n) {
            if (i != j) {
                sum += a[j];
            }
        }

        rep1(j, maxn - 1) {
            // iterating over all possible values for tina
            int sum2 = sum + j;
            if (sum2 & 1) conts;

            if (curr[sum2 / 2]) {
                cnt[j]++;
            }
            else if (sum2 / 2 - j >= 0) {
                if (curr[sum2 / 2 - j]) {
                    cnt[j]++;
                }
            }
        }
    }

    vector<int> ans;

    rep1(i, maxn - 1) {
        if (cnt[i] == n) {
            ans.pb(i);
        }
    }

    cout << sz(ans) << endl;
    trav(x, ans) cout << x << " ";
    cout << endl;
}

int main()
{
    fastio;

    int t = 1;
    // cin >> t;
    rep1(i, t) {
        solve(i);
    }

    return 0;
}

Compilation message (stderr)

bootfall.cpp: In function 'void usaco(std::string)':
bootfall.cpp:64:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   64 |     freopen((filename + ".in").c_str(), "r", stdin);
      |     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
bootfall.cpp:65:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   65 |     freopen((filename + ".out").c_str(), "w", stdout);
      |     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 6 / 6
• Subtask 2: 7 / 7
• Subtask 3: 15 / 15
• Subtask 4: 16 / 16
• Subtask 5: 21 / 21
• Subtask 6: 35 / 35