Submission #1042623

#	Time	Username	Problem	Language	Result	Execution time	Memory
1042623		Theo830	Flooding Wall (BOI24_wall)	C++17	0 / 100	488 ms	1048576 KiB

Main

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const ll INF = 1e9+7;
const ll MOD = 998244353;
typedef pair<ll,ll> ii;
#define iii pair<ii,ll>
#define f(i,a,b) for(ll i = a;i < b;i++)
#define pb push_back
#define vll vector<ll>
#define F first
#define S second
#define all(x) (x).begin(), (x).end()
///I hope I will get uprating and don't make mistakes
///I will never stop programming
///sqrt(-1) Love C++
///Please don't hack me
///@TheofanisOrfanou Theo830
///Think different approaches (bs,dp,greedy,graphs,shortest paths,mst)
///Stay Calm
///Look for special cases
///Beware of overflow and array bounds
///Think the problem backwards
///Training
int main(void){
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    ll n;
    cin>>n;
    ll a[n],b[n];
    f(i,0,n){
        cin>>a[i];
    }
    f(i,0,n){
        cin>>b[i];
        if(b[i] < a[i]){
            swap(a[i],b[i]);
        }
    }
    ll mpl[n][1005];
    ll mpr[n][1005];
    f(i,0,n){
        f(j,0,1005){
            mpl[i][j] = mpr[i][j] = 0;
        }
    }
    mpl[0][a[0]] = mpl[0][b[0]] = mpr[n-1][a[n-1]] = mpr[n-1][b[n-1]] = 1;
    f(i,1,n){
        f(j,0,1005){
            mpl[i][max(j,a[i])] += mpl[i-1][j];
            mpl[i][max(j,b[i])] += mpl[i-1][j];
            if(mpl[i][max(j,a[i])] >= INF){
               mpl[i][max(j,a[i])] -= INF;
            }
            if(mpl[i][max(j,b[i])] >= INF){
               mpl[i][max(j,b[i])] -= INF;
            }
        }
    }
    ll ans = 0;
    for(ll i = n-2;i >= 0;i--){
        f(j,0,1005){
            mpr[i][max(j,a[i])] += mpr[i+1][j];
            mpr[i][max(j,b[i])] += mpr[i+1][j];
            if(mpr[i][max(j,a[i])] >= INF){
               mpr[i][max(j,a[i])] -= INF;
            }
            if(mpr[i][max(j,b[i])] >= INF){
               mpr[i][max(j,b[i])] -= INF;
            }
        }
    }
    f(i,1,n-1){
        ll sum = 0;
        for(ll j = 1000;j >= 1;j--){
            sum += mpl[i-1][j];
            if(sum >= INF){
                sum -= INF;
            }
            ll posa = sum * mpr[i+1][j];
            posa %= INF;
            if(a[i] < j){
                ans += (j - a[i]) * posa;
                ans %= INF;
            }
            if(b[i] < j){
                ans += (j - b[i]) * posa;
                ans %= INF;
            }
        }
    }
    cout<<ans<<"\n";
}

• Subtask 1: 0 / 8
• Subtask 2: 0 / 17
• Subtask 3: 0 / 19
• Subtask 4: 0 / 14
• Subtask 5: 0 / 12
• Subtask 6: 0 / 30