Submission #1212972

#	Time	Username	Problem	Language	Result	Execution time	Memory
1212972		goulthen	Fancy Fence (CEOI20_fancyfence)	C++20	100 / 100	15 ms	4032 KiB

fancyfence

//#pragma GCC optimize("O3")
//#pragma GCC optimize("unroll-loops")
#include <bits/stdc++.h>
using namespace std;
#include <ext/pb_ds/assoc_container.hpp>
using namespace __gnu_pbds;
template <class T>
using Tree =
    tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;

#define int long long
#define ll long long
#define pii pair<int, int>
#define pll pair<ll, ll>
#define fi first
#define se second
#define rep(i, a, b) for (int i = a; i <= b; ++i)
#define per(i, b, a) for (int i = b; i >= a; --i)
#define pb push_back
#define eb emplace_back
#define all(v) (v).begin(), (v).end()
#define lsb(x) (x)&(-x)
 
void setIO(string name = "") {
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);cout.tie(nullptr);
    if (!name.empty()) {
        freopen((name + ".in").c_str(), "r", stdin);
        freopen((name + ".out").c_str(), "w", stdout);
    }
}
ll fexp(ll a, ll b, ll m) {
    if (b == 0) return 1LL;
    ll p = a;
    ll ans = 1;
 
    while (b > 0) {
        if (b % 2 != 0) ans = (ans*p)%m;
        p = (p*p)%m;
        b >>= 1;
    }
    return ans;
}
 
const int MAXN = 2e5 + 10;
const int INF = 1e18+5;
const int MOD = 1e9+7;
int w[MAXN], h[MAXN];

int ch(int x) {
    x = x%MOD;
    return (((x*(x+1))%MOD)*500000004)%MOD;
}

void solve() {
    int n;cin >> n;
    vector<pii> rd;
    rep(i,1,n) cin >> h[i];
    rep(i,1,n) cin >> w[i];

    int ans = 0;
    rep(i,1,n) {
        int acc = w[i], acc2 = 0;
        while (!rd.empty()) {
            auto [cw,oh] = rd.back();
            if (oh < h[i]) break;
            rd.pop_back();
            acc=(acc+cw)%MOD;
            ans = (ans - ch(acc2)*(ch(oh) - ch(h[i])))%MOD;
            ans = (ans+MOD)%MOD;
            acc2 = (acc2+cw)%MOD;
            ans = (ans + ch(acc2)*(ch(oh) - ch(h[i])))%MOD;
        }
        rd.pb({acc,h[i]});
    }
    n = rd.size();
    //cout << ans << '\n';

    int acc = 0;
    per(i,n-1,0) {
        auto [W,H] = rd[i];
        ans = (ans - ch(acc)*ch(H))%MOD;
        ans = (ans+MOD)%MOD;
        acc = (acc+W)%MOD;
        ans = (ans + ch(acc)*ch(H))%MOD;
    }
    cout << ans << '\n';
}


int32_t main() {
    setIO();
    int tt = 1;
    //cin >> tt;

    while (tt-- > 0) solve();
    
}

Compilation message (stderr)

fancyfence.cpp: In function 'void setIO(std::string)':
fancyfence.cpp:28:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   28 |         freopen((name + ".in").c_str(), "r", stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
fancyfence.cpp:29:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   29 |         freopen((name + ".out").c_str(), "w", stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

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