Submission #111237

#	Time	Username	Problem	Language	Result	Execution time	Memory
111237		tictaccat	Boat (APIO16_boat)	C++14	100 / 100	418 ms	11128 KiB

boat

#include <bits/stdc++.h>

using namespace std;

#define int long long

const int MAX = 1000 + 5;
const int MOD = 1e9 + 7;
const int INV2 = 5e8 + 4;

int N,ans;
vector<int> a(MAX), b(MAX), ways(2*MAX), newWays(2*MAX), bin; //ways[i] = ways of ending between bin[i] and bin[i+1]-1
vector<vector<int>> Z(MAX), val(MAX,vector<int>(MAX));
vector<int> invs(MAX,-1);

int exp(int a, int e) {
    if (e == 0) return 1;
    if (e%2 == 1) return a * exp(a,e-1) % MOD;
    int temp = exp(a,e/2);
    return temp * temp % MOD;
}

int inv(int k) {
    return exp(k,MOD-2);
}

int pre(int k) {
    int res = 0;
    int sz = bin[k+1] - bin[k];
    val[k][0] = 1;
    for (int i = 1; i <= N; i++) {
        val[k][i] = val[k][i-1] * (sz+i-1) % MOD * inv(i) % MOD;
    }
    return res;
}

int calc(int k) {
    int res = 0;
    for (int i = 1; i <= Z[k].size(); i++) {
        res += val[k][i] * Z[k][Z[k].size()-i] % MOD;
        res %= MOD;
    }
    return res;
}

main() {

    cin >> N;

    for (int i = 0; i < N; i++) {
        cin >> a[i] >> b[i];
        b[i]++;
        bin.push_back(a[i]);
        bin.push_back(b[i]);
    }

    bin.push_back(2);

    sort(bin.begin(),bin.end());
    bin.erase(unique(bin.begin(),bin.end()),bin.end());

    for (int i = 0; i < bin.size(); i++) pre(i);

    for (int i = 0; i < N; i++) {
      //  cout << i << "\n";
        int pre = 1, k = 0; 
        for (; bin[k] < a[i]; k++) {pre += ways[k]; pre %= MOD;}
        for (; k+1 < bin.size() && bin[k+1] <= b[i]; k++) {
            Z[k].push_back(pre);
            newWays[k] = calc(k);
            pre += ways[k];
            pre %= MOD;
        }
        ways = newWays;
        //cout << ways[0] << "\n";
    }

    for (int k = 0; k < bin.size()-1; k++) {ans += ways[k]; ans %= MOD;}

    cout << (ans < 0 ? ans + MOD : ans) << "\n";

    return 0;
}

Compilation message (stderr)

boat.cpp: In function 'long long int calc(long long int)':
boat.cpp:39:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for (int i = 1; i <= Z[k].size(); i++) {
                     ~~^~~~~~~~~~~~~~
boat.cpp: At global scope:
boat.cpp:46:6: warning: ISO C++ forbids declaration of 'main' with no type [-Wreturn-type]
 main() {
      ^
boat.cpp: In function 'int main()':
boat.cpp:62:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for (int i = 0; i < bin.size(); i++) pre(i);
                     ~~^~~~~~~~~~~~
boat.cpp:68:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         for (; k+1 < bin.size() && bin[k+1] <= b[i]; k++) {
                ~~~~^~~~~~~~~~~~
boat.cpp:78:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for (int k = 0; k < bin.size()-1; k++) {ans += ways[k]; ans %= MOD;}
                     ~~^~~~~~~~~~~~~~

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