Submission #278534

#	Time	Username	Problem	Language	Result	Execution time	Memory
278534		BeanZ	Boat (APIO16_boat)	C++14	9 / 100	475 ms	4352 KiB

boat

#include <bits/stdc++.h>

using namespace std;

#define ll long long
#define endl '\n'
ll dp[1005][505], inv[2005], l[505], r[505];
const int mod = 1e9 + 7;
int main(){
        ios_base::sync_with_stdio(false);
        cin.tie(0);
        if (fopen("VietCT.INP", "r")){
                freopen("VietCT.INP", "r", stdin);
                freopen("VietCT.OUT", "w", stdout);
        }
        ll n;
        cin >> n;
        inv[1] = 1;
        for (int i = 2; i < 2000; i++) inv[i] = (mod / i) * (mod - inv[mod % i]) % mod;
        vector<ll> val;
        for (int i = 1; i <= n; i++){
                cin >> l[i] >> r[i];
                val.push_back(l[i]);
                r[i]++;
                val.push_back(r[i]);
        }
        sort(val.begin(), val.end());
        val.resize(unique(val.begin(), val.end()) - val.begin());
        for (int i = 1; i <= n; i++){
                l[i] = lower_bound(val.begin(), val.end(), l[i]) - val.begin() + 1;
                r[i] = lower_bound(val.begin(), val.end(), r[i]) - val.begin() + 1;
        }
        dp[0][0] = 1;
        for (int i = 1; i < val.size(); i++){
                dp[i][0] = 1;
                for (int j = 1; j <= n; j++){
                        dp[i][j] = dp[i - 1][j];
                        if (i < l[j] || i >= r[j]) continue;
                        ll s = val[i] - val[i - 1];
                        ll cnt = 1;
                        ll p = s;
                        for (int k = j - 1; k >= 0; k--){
                                dp[i][j] = (dp[i][j] + dp[i - 1][k] * p) % mod;
                                p = p * (s + cnt) % mod;
                                p = p * inv[cnt + 1] % mod;
                                cnt++;
                        }
                }
        }
        ll ans = 0;
        for (int i = 1; i <= n; i++){
                ans = (ans + dp[val.size() - 1][i]) % mod;
        }
        cout << ans;
}

Compilation message (stderr)

boat.cpp: In function 'int main()':
boat.cpp:34:27: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<long long int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   34 |         for (int i = 1; i < val.size(); i++){
      |                         ~~^~~~~~~~~~~~
boat.cpp:13:24: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result]
   13 |                 freopen("VietCT.INP", "r", stdin);
      |                 ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~
boat.cpp:14:24: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result]
   14 |                 freopen("VietCT.OUT", "w", stdout);
      |                 ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~

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