Submission #1062069

#	Time	Username	Problem	Language	Result	Execution time	Memory
1062069		Jarif_Rahman	Flooding Wall (BOI24_wall)	C++17	58 / 100	5065 ms	10076 KiB

Main

#include <bits/stdc++.h>
#define pb push_back
#define f first
#define sc second
using namespace std;
typedef long long int ll;
typedef string str;

const ll md = 1e9+7;
const int N = 5e5+5;
const ll inv2 = 500000004;
ll pw2[N];

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

    pw2[0] = 1;
    for(int i = 1; i < N; i++) pw2[i] = (pw2[i-1]*2)%md;

    int n; cin >> n;
    vector<int> A(n), B(n);
    int m = 0;
    for(int &x: A) cin >> x, m = max(m, x);
    for(int &x: B) cin >> x, m = max(m, x);
    for(int i = 0; i < n; i++) if(A[i] > B[i]) swap(A[i], B[i]);

    ll ans = 0;

    auto solve = [&](int i, ll x){
        ll cur = 1, sum = 0;
        int c = 0;
        for(int j = i-1; j >= 0; j--){
            if(A[j] > x){
                cur = 0;
                break;
            }
            if(B[j] <= x) c++;
        }
        cur*=pw2[c], cur%=md;
        cur*=pw2[n-i-1], cur%=md;

        bool breaked = 0;
        for(int j = i+1; j < n; j++){
            if(B[j] < x) continue;
            if(A[j] >= x){
                ans+=((((j-i)*x)%md)*cur)%md, ans%=md;
                breaked = 1;
                break;
            }
            cur*=inv2, cur%=md;
            ans+=((((j-i)*x)%md)*cur)%md, ans%=md;
        }
        if(!breaked) ans+=(x*cur)%md, ans%=md;
    };

    auto solve_rev = [&](int i, ll x){
        ll cur = 1, sum = 0;
        int c = 0;
        for(int j = i+1; j < n; j++){
            if(A[j] >= x){
                cur = 0;
                break;
            }
            if(B[j] < x) c++;
        }
        cur*=pw2[c], cur%=md;
        cur*=pw2[i], cur%=md;

        for(int j = i-1; j >= 0; j--){
            if(B[j] <= x) continue;
            if(A[j] > x){
                ans+=((((i-j)*x)%md)*cur)%md, ans%=md;
                break;
            }
            cur*=inv2, cur%=md;
            ans+=((((i-j)*x)%md)*cur)%md, ans%=md;
        }
    };

    for(int i = 0; i < n; i++){
        solve(i, A[i]);
        solve(i, B[i]);
        solve_rev(i, A[i]);
        solve_rev(i, B[i]);
    }

    for(int i = 0; i < n; i++) ans-=((A[i]+B[i])*pw2[n-1])%md, ans%=md;
    if(ans < 0) ans+=md;

    cout << ans << "\n";
}

Compilation message (stderr)

Main.cpp: In lambda function:
Main.cpp:31:21: warning: unused variable 'sum' [-Wunused-variable]
   31 |         ll cur = 1, sum = 0;
      |                     ^~~
Main.cpp: In lambda function:
Main.cpp:58:21: warning: unused variable 'sum' [-Wunused-variable]
   58 |         ll cur = 1, sum = 0;
      |                     ^~~

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