Submission #970696

#	Time	Username	Problem	Language	Result	Execution time	Memory
970696		VinhLuu	Boat (APIO16_boat)	C++17	0 / 100	4 ms	4440 KiB

boat

//#pragma GCC optimize("O3,unroll-loops")
//#pragma GCC target("avx2,bmi,bmi2,lzcnt,popcnt")
#include <bits/stdc++.h>
#define ll long long
#define fi first
#define se second
#define pb push_back
#define all(lmao) lmao.begin(), lmao.end()

using namespace std;

typedef pair<int,int> pii;
typedef tuple<int,int,int> tp;
const int N = 505;
int block = 555;
const int mod = 1e9 + 7;
//const ll oo = 5e18;

int n, L[N], R[N];
ll f[N][N], inv[N];

ll lt(ll u,ll v){
    if(v == 0) return 1;
    ll x = u, kq = 1;
    while(v){
        if(v & 1) kq = kq * x % mod;
        x = x * x % mod;
        v /= 2;
    }
    return kq;
}

signed main(){
    ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);

    #define task "v"
    if(fopen(task ".inp","r")){
        freopen(task ".inp","r",stdin);
        freopen(task ".out","w",stdout);
    }

    cin >> n;
    vector<int> rrh;
    for(int i = 1; i <= n; i ++){
        cin >> L[i] >> R[i];
        rrh.pb(L[i]);
        rrh.pb(R[i] + 1);
    }
    sort(all(rrh)); rrh.resize(unique(all(rrh)) - rrh.begin());

//    for(auto j : rrh) cerr << j << " t\n";

    inv[0] = f[0][0] = 1;
    for(int i = 1; i <= n; i ++) f[0][i] = 1, inv[i] = lt(i, mod - 2);

    for(int i = 1; i < rrh.size(); i ++){
//        cerr << i << " h\n";
        for(int j = 1; j <= n; j ++) if(L[j] <= rrh[i - 1] && rrh[i - 1] <= R[j]){
            f[i][j] = f[i - 1][j];
            ll w = rrh[i] - rrh[i - 1], pick = 1;
            for(int k = 1; k <= j; k ++){
                if(L[j - k + 1] <= rrh[i - 1] && rrh[i - 1] <= R[j - k + 1]){
                    if(k <= w) pick = pick * (w - k + 1) % mod * inv[k] % mod;
                    f[i][j] = (f[i][j] + f[i - 1][j - k] * pick % mod) % mod;
                }else f[i][j] = (f[i][j] + f[i - 1][j - k] * pick % mod) % mod;
            }
//            cerr << i << " " << j << " " << f[i][j] << " k\n";
        }else{
            f[i][j] = f[i - 1][j];
//            cerr << i << " " << j << " " << f[i][j] << " k\n";
        }
    }
    ll ans = 0;
    for(int i = 1; i <= n; i ++) ans = (ans + f[rrh.size() - 1][i]) % mod;
    cout << ans;
}

Compilation message (stderr)

boat.cpp: In function 'int main()':
boat.cpp:56:22: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   56 |     for(int i = 1; i < rrh.size(); i ++){
      |                    ~~^~~~~~~~~~~~
boat.cpp:38:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   38 |         freopen(task ".inp","r",stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~
boat.cpp:39:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   39 |         freopen(task ".out","w",stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~

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