Submission #362638

#	Time	Username	Problem	Language	Result	Execution time	Memory
362638		valerikk	Packing Biscuits (IOI20_biscuits)	C++17	42 / 100	1086 ms	22168 KiB

biscuits

#include <bits/stdc++.h>
 
using namespace std; 
 
typedef long long ll;
 
// O(kx)
// O(qklogx)

ll count_tastiness(ll x, vector<ll> a) {
    int k = 60;
    while ((int)a.size() < k + 1) a.push_back(0);
    for (int i = 0; i < k; i++) {
        ll z = max(0LL, a[i] - x) / 2;
        a[i + 1] += z;
        a[i] -= 2 * z;
    }
    if (x <= 10000) {
        int C = x + 2;
        vector<ll> dp(C, 0);
        dp[0] = 1;
        for (int i = 0; i < k; i++) {
            vector<ll> ndp(C, 0);
            for (int carry = 0; carry < C; carry++) {
                int cur = carry + a[i];
                ndp[cur / 2] += dp[carry];
                if (cur >= x) ndp[(cur - x) / 2] += dp[carry];
            }
            dp.swap(ndp);
        }
        ll res = 0;
        for (const ll &z : dp) res += z;
        return res;
    }
    ll sum = 0;
    for (const ll &z : a) sum += z;
    if (sum <= 100000) {
        ll res = 0;
        for (ll y = 0; y <= 100000; y++) {
            auto a_copy = a;
            bool can = true;
            for (int i = 0; i < k; i++) {
                ll need = x * ((y >> i) & 1);
                if (a[i] < need) {
                    can = false;
                    break;
                }
                a[i] -= need;
                a[i + 1] += a[i] / 2;
            }
            if (can) res++;
            a = a_copy;
        }
        return res;
    }
    vector<pair<ll, ll>> dp;
    dp.emplace_back(0, 1);
    for (int i = 0; i < k; i++) {
        vector<pair<ll, ll>> ndp_no_add, ndp_add;
        for (const auto &[carry, ways] : dp) {
            int cur = a[i] + carry;
            ndp_no_add.emplace_back(cur / 2, ways);
            if (cur >= x) ndp_add.emplace_back((cur - x) / 2, ways);
        }
        vector<pair<ll, ll>> tmp;
        merge(ndp_no_add.begin(), ndp_no_add.end(), ndp_add.begin(), ndp_add.end(), back_inserter(tmp));
        vector<pair<ll, ll>> ndp;
        for (const auto &[carry, ways] : tmp) {
            if (ndp.empty() || carry != ndp.back().first) ndp.emplace_back(carry, ways); else ndp.back().second += ways;
        } 
        dp.swap(ndp);
    }
    ll res = 0;
    for (const auto &[carry, ways] : dp) res += ways;
    return res;
}
 
#ifdef LOCAL
int main() {
    freopen("input.txt", "r", stdin);
    ios::sync_with_stdio(false);
    cin.tie(0);
    int k;
    ll x;
    cin >> k >> x;
    vector<ll> a(k);
    for (ll &z : a) cin >> z;
    cout << count_tastiness(x, a);
    return 0;
}
#endif

• Subtask 1: 9 / 9
• Subtask 2: 12 / 12
• Subtask 3: 21 / 21
• Subtask 4: 0 / 35
• Subtask 5: 0 / 23