Submission #1145488

#	Time	Username	Problem	Language	Result	Execution time	Memory
1145488		antonn	Flooding Wall (BOI24_wall)	C++17	44 / 100	5093 ms	10052 KiB

Main

#include <bits/stdc++.h>
#pragma GCC optimize ("Ofast")

#define F first
#define S second
 
using namespace std;
using ll = long long;
using pi = pair<int, int>;
using vi = vector<int>;
 
template<class T> bool ckmin(T& a, T b) { return b < a ? a = b, true : false; }
template<class T> bool ckmax(T& a, T b) { return a < b ? a = b, true : false; } 

const int N = 5e5 + 7;
const int M = 1e9 + 7;

int add(int a, int b) {
    a += b;
    if (a >= M) a -= M;
    if (a < 0) a += M;
    return a;
}

int mul(int a, int b) {
    return (ll) a * b % M;
}

int mul(int a, int b, int c) {
    return mul(a, mul(b, c));
}

int mul(int a, int b, int c, int d) {
    return mul(a, mul(b, c, d));
}

int n, a[N], b[N], c[N];
int pref[N], suff[N];

int pw2[N];

ll f(int p, int x) {
    ll ans = 0;
    {
        int ways = 1;
        for (int i = 1; i < p; ++i) ways = mul(ways, (x >= a[i]) + (x >= b[i]));
        
        suff[n+1] = 1;
        for (int i = n; i >= 1; --i) suff[i] = mul(suff[i+1], (a[i] < x) + (b[i] < x));
        
        int inter = 1;
        for (int i = p + 1; i <= n; ++i) {
            int s = add(pw2[n-i], -suff[i+1]);
            if (x >= a[i]) ans = add(ans, mul(x - a[i], ways, s, inter));
            if (x >= b[i]) ans = add(ans, mul(x - b[i], ways, s, inter));
            
            inter = mul(inter, (x > a[i]) + (x > b[i]));
        }
    }
    {
        int ways = 1;
        for (int i = n; i > p; --i) ways = mul(ways, (x >= a[i]) + (x >= b[i]));
        
        pref[0] = 1;
        for (int i = 1; i <= n; ++i) pref[i] = mul(pref[i - 1], (a[i] <= x) + (b[i] <= x));
        
        int inter = 1;
        for (int i = p - 1; i >= 1; --i) {
            int s = add(pw2[i - 1], -pref[i - 1]);
            if (x >= a[i]) ans = add(ans, mul(x - a[i], ways, s, inter));
            if (x >= b[i]) ans = add(ans, mul(x - b[i], ways, s, inter));
            
            inter = mul(inter, (x > a[i]) + (x > b[i]));
        }
    }
    
    return ans;
}

int main() {
    ios::sync_with_stdio(0); cin.tie(0);
    
    cin >> n;
    for (int i = 1; i <= n; ++i) cin >> a[i];
    for (int i = 1; i <= n; ++i) cin >> b[i];
    
    pw2[0] = 1;
    for (int i = 1; i < N; ++i) pw2[i] = mul(pw2[i - 1], 2);
    
    ll ans = 0;
    for (int i = 1; i <= n; ++i) { 
        ans += f(i, a[i]); if (ans >= M) ans -= M;
        ans += f(i, b[i]); if (ans >= M) ans -= M;
    }
    cout << ans << "\n";
}

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