Submission #930721

#	Time	Username	Problem	Language	Result	Execution time	Memory
930721		LucaIlie	Fancy Fence (CEOI20_fancyfence)	C++17	55 / 100	64 ms	3288 KiB

fancyfence

#include <bits/stdc++.h>

using namespace std;

const int MAX_N = 1e5;
const int MOD = 1e9 + 7;
int h[MAX_N], w[MAX_N], p[MAX_N];
vector <int> s;

int lgPut( int x, int n ) {
    if ( n == 0 )
        return 1;

    int p = lgPut( x, n / 2 );
    p = (long long)p * p % MOD;
    if ( n % 2 == 1 )
        p = (long long)p * x % MOD;

    return p;
}

const int inv2 = (MOD + 1) / 2;
int nchoose2( int n ) {
    return (long long)n * (n + 1) % MOD * inv2 % MOD;
}

int main() {
    int n;

    cin >> n;
    for ( int i = 0; i < n; i++ )
        cin >> h[i];
    for ( int i = 0; i < n; i++ )
        cin >> w[i];


    int ans = 0, sum = 0;
    for ( int i = 0; i < n; i++ ) {
        while ( !s.empty() && h[i] < h[s.back()] ) {
            sum = (sum - (long long)nchoose2( h[s.back()] ) * p[s.back()] % MOD + MOD) % MOD;
            p[i] = (p[i] + p[s.back()]) % MOD;
            s.pop_back();
        }
        s.push_back( i );

        sum = (sum + (long long)nchoose2( h[i] ) * p[i]) % MOD;
        ans = (ans + (long long)nchoose2( h[i] ) * nchoose2( w[i] )) % MOD;
        ans = (ans + (long long)sum * w[i]) % MOD;
        sum = (sum + (long long)nchoose2( h[i] ) * w[i]) % MOD;

        p[i] += w[i];
    }

    cout << ans << "\n";

    return 0;
}

• Subtask 1: 0 / 0
• Subtask 2: 12 / 12
• Subtask 3: 13 / 13
• Subtask 4: 15 / 15
• Subtask 5: 15 / 15
• Subtask 6: 0 / 18
• Subtask 7: 0 / 27