Submission #839828

#	Time	Username	Problem	Language	Result	Execution time	Memory
839828		popovicirobert	Boat (APIO16_boat)	C++14	9 / 100	3 ms	3540 KiB

boat

#include <bits/stdc++.h>
 
using namespace std;

constexpr int MOD = (int) 1e9 + 7;
constexpr int INF = (int) 2e9;

 
int main() {
#ifdef HOME
    ifstream cin("input.in");
    ofstream cout("output.out");
#endif
    ios::sync_with_stdio(false);
    cin.tie(0), cout.tie(0);

    int n;
    cin >> n;
    
    vector<int> a(n + 1), b(n + 1);
    vector<int> x;

    for (int i = 1; i <= n; i++) {
        cin >> a[i] >> b[i];
        x.push_back(a[i]);
        x.push_back(b[i]);
    }

    sort(x.begin(), x.end());
    x.resize(unique(x.begin(), x.end()) - x.begin());

    vector<pair<int, int>> segs;
    segs.push_back({0, 0});

    for (int i = 0; i < (int)x.size(); i++) {
        segs.push_back({x[i], x[i]});
        if (i + 1 < (int)x.size()) {
            if (x[i] + 1 <= x[i + 1] - 1) {
                segs.push_back({x[i] + 1, x[i + 1] - 1});
            }
        }
    }

    // for (auto itr : segs) {
    //     cerr << itr.first << " " << itr.second << "    "; 
    // }
    // cerr << "\n";

    vector<vector<int>> dp(n + 1, vector<int>(segs.size()));
    dp[0][0] = 1;

    for (int i = 1; i <= n; i++) {
        for (int j = 0; j < (int)segs.size(); j++) {
            dp[i][j] = dp[i - 1][j];
        }

        int low = 0, sum = 0;
        while (!(a[i] <= segs[low].first && segs[low].second <= b[i])) {
            if (low > 0) {
                sum += dp[i - 1][low - 1];
                if (sum >= MOD)
                    sum -= MOD;
            }
            low++;
        }

        
        while (low < (int)segs.size() && a[i] <= segs[low].first && segs[low].second <= b[i]) {
            if (low > 0) {
                sum += dp[i - 1][low - 1];
                if (sum >= MOD)
                    sum -= MOD;
            }
            dp[i][low] = (dp[i][low] + 1LL * (segs[low].second - segs[low].first + 1) * sum) % MOD;
            low++;
        }

        // for (int j = 0; j < segs.size(); j++) {
        //     cerr << dp[i][j] << " ";
        // }
        // cerr << "\n";
    }

    int answer = 0;
    for (int i = 1; i < (int)segs.size(); i++) {
        answer += dp[n][i];
        if (answer >= MOD)
            answer -= MOD;
    }

    cout << answer;
 
    return 0;
}

• Subtask 1: 9 / 9
• Subtask 2: 0 / 22
• Subtask 3: 0 / 27
• Subtask 4: 0 / 42