Submission #96115

#	Time	Username	Problem	Language	Result	Execution time	Memory
96115		oolimry	Boat (APIO16_boat)	C++14	58 / 100	2055 ms	16376 KiB

boat

#include <bits/stdc++.h>

using namespace std;
typedef pair<long long, long long> ii;
long long mod = 1000000007;
//long long dp[505][2005];
//static long long dp[505][2005][505];
#define int long long
long long modInverse(long long a, long long m)
{
    long long m0 = m;
    long long y = 0, x = 1;

    if (m == 1)
      return 0;

    while (a > 1)
    {
        // q is quotient
        long long q = a / m;
        long long t = m;

        // m is remainder now, process same as
        // Euclid's algo
        m = a % m, a = t;
        t = y;

        // Update y and x
        y = x - q * y;
        x = t;
    }

    // Make x positive
    if (x < 0)
       x += m0;

    return x;
}
main()
{
    //freopen("i.txt","r",stdin);
    ios_base::sync_with_stdio(false);
    long long inverse[505];
    for(long long i = 1;i < 505;i++){
        inverse[i] = modInverse(i,mod);
    }
    int n;
    cin >> n;
    long long a[n];
    long long b[n];

    set<long long> s;
    for(int i = 0;i < n;i++){
        cin >> a[i] >> b[i];
        s.insert(a[i]);
        s.insert(b[i]);
    }
    //cout << s.size() << endl;
    vector<long long> key;
    for(set<long long>::iterator it = s.begin();it != s.end();it++){
        key.push_back(*it);
    }
    //cout << k.size() << endl;
    vector<ii> ranges;
    for(int i = 0;i < key.size();i++){
        ranges.push_back(ii(key[i],key[i]));
        if(i != 0){
            if(key[i] != key[i-1]+1){
                ranges.push_back(ii(key[i-1]+1,key[i]-1));
            }
        }
    }
    sort(ranges.begin(),ranges.end());
    int m = ranges.size();
    //cout << m << "\n";
    long long diff[m];
    for(int i = 0;i < m;i++){
        diff[i] = ranges[i].second - ranges[i].first + 1;
        diff[i] %= mod;
        //cout << ranges[i].first << " " << ranges[i].second << "\n";
    }
    long long posa[n];
    long long posb[n];
    for(int i = 0;i < n;i++){
        for(int j = 0;j < m;j++){
            if(ranges[j].first == a[i]) posa[i] = j;
            if(ranges[j].second == b[i]) posb[i] = j;
        }
    }



    static long long dp[2][2005][505];
    //boat no, range, number taken b4;

    for(int i = 0;i < 2;i++){
        for(int j = 0;j < m;j++){
            for(int k = 0;k < 505;k++){
                dp[i][j][k] = 0ll;
            }
        }
    }


    for(int j = posa[0];j <= posb[0];j++){
        if(a[0] <= ranges[j].first && b[0] >= ranges[j].second){
            dp[0][j][1] = diff[j];
            //cout << a[0] << " " << ranges[j].first << " " << ranges[j].second << " " << b[0] << endl;
        }
    }

    for(int i = 1;i < n;i++){
        ///take nothing for this school
        int ii = i % 2;
        for(int j = 0;j < m;j++){
            for(int k = 1;k < 505;k++){
                if(dp[ii^1][j][k] == 0) break;
                dp[ii][j][k] = dp[ii^1][j][k];
                dp[ii][j][k] %= mod;
            }
        }

        ///take same as previous school
        for(int j = posa[i];j <= posb[i];j++){
            if(a[i] <= ranges[j].first && b[i] >= ranges[j].second){
                for(int k = 2;k < 505;k++){
                    long long x = dp[ii^1][j][k-1];
                    if(diff[j] - k + 1 <= 0) break;
                    x *= (diff[j] - k + 1);
                    x %= mod;
                    x *= inverse[k];
                    x %= mod;
                    dp[ii][j][k] += x;
                    //dp[ii][j][k] %= mod;
                }
            }
        }

        ///take for the first time

        long long acc = 0ll;
        for(int j = 0;j < m;j++){
            if(j != 0){
                for(int k = 1;k < 505;k++){
                    if(dp[ii^1][j-1][k] == 0) break;
                    acc += dp[ii^1][j-1][k];
                    acc %= mod;
                }
            }
            if(a[i] <= ranges[j].first && b[i] >= ranges[j].second){
                long long x = acc;
                x += 1;
                x *= diff[j];
                acc %= mod;
                dp[ii][j][1] += x;
                dp[ii][j][1] %= mod;
            }
        }

    }

/*
    for(int j = 0;j < m;j++){
        cout << ranges[j].first << " " << ranges[j].second << ": ";
        for(int i = 0;i < n;i++){
            cout << dp[i][j] << " ";
        }
        cout << "\n";
    }
*/
    long long ans = 0ll;
    for(int j = 0;j < m;j++){
        for(int k = 1;k < 505;k++){
            ans += dp[(n-1)%2][j][k];
            ans %= mod;
            if(dp[(n-1)%2][j][k] != 0){
                //cout << j << " " << k << " " << dp[(n-1)%2][j][k] << "\n";
            }
        }
    }
    cout << ans;

    return 0;
}

Compilation message (stderr)

boat.cpp:39:6: warning: ISO C++ forbids declaration of 'main' with no type [-Wreturn-type]
 main()
      ^
boat.cpp: In function 'int main()':
boat.cpp:65:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for(int i = 0;i < key.size();i++){
                   ~~^~~~~~~~~~~~

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