Submission #1165442

#	Time	Username	Problem	Language	Result	Execution time	Memory
1165442		SmuggingSpun	Fancy Fence (CEOI20_fancyfence)	C++20	100 / 100	25 ms	3144 KiB

fancyfence

#include<bits/stdc++.h>
#define taskname "A"
using namespace std;
typedef long long ll;
const int lim = 1e5 + 5;
const int mod = 1e9 + 7;
void add(int& a, int b){
    if((a += b) >= mod){
        a -= mod;
    }
}
int f(ll N){
    return ((N & 1LL) ? N % mod * (((N + 1) >> 1LL) % mod) : (N >> 1LL) % mod * ((N + 1) % mod)) % mod;
}
int f(ll l, ll r){
    return (f(r) - f(l - 1) + mod) % mod;
}
int n, h[lim], w[lim];
namespace sub3{
    void solve(){
        int ans = f(accumulate(w + 1, w + n + 1, 0LL));
        ll N = 0;
        for(int i = 1; i <= n; i++){
            if(h[i] == 2){
                N += w[i];
            }
            else{
                add(ans, (f(N) << 1) % mod);
                N = 0;
            }
        }
        cout << (ans + ((f(N) << 1) % mod)) % mod;
    }
}
namespace sub4{
    void solve(){
        cout << 1LL * f(accumulate(w + 1, w + n + 1, 0LL)) * f(h[1]) % mod;
    }
}
namespace sub2567{
    ll len[lim];
    int par[lim];
    int find_set(int N){
        return N == par[N] ? N : par[N] = find_set(par[N]);
    }    
    void merge(int a, int b){
        if(len[a = find_set(a)] != 0 && len[b = find_set(b)] != 0){
            len[par[b] = a] += len[b];
        }
    }
    void solve(){
        memset(len, 0, sizeof(len));
        vector<int>p(n);
        iota(p.begin(), p.end(), 1);
        sort(p.begin(), p.end(), [&] (int i, int j){
            return h[i] > h[j];
        });
        int ans = 0;
        iota(par, par + n + 2, 0);
        for(int& i : p){
            int left = len[find_set(i - 1)] % mod, right = len[find_set(i + 1)] % mod;
            add(ans, 1LL * left * (len[i] = w[i]) % mod * f(h[i]) % mod);
            add(ans, 1LL * right * w[i] % mod * f(h[i]) % mod);
            add(ans, 1LL * left * right % mod * f(h[i]) % mod);
            add(ans, 1LL * f(w[i]) * f(h[i]) % mod);
            merge(i, i + 1);
            merge(i, i - 1);
        }
        cout << ans;
    }
}
int main(){
    ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
    if(fopen(taskname".inp", "r")){
        freopen(taskname".inp", "r", stdin);
    }
    cin >> n;
    for(int i = 1; i <= n; i++){
        cin >> h[i];
    }
    for(int i = 1; i <= n; i++){
        cin >> w[i];
    }
    if(*max_element(h + 1, h + n + 1) < 3){
        sub3::solve();
    }
    else if(*min_element(h + 1, h + n + 1) == *max_element(h + 1, h + n + 1)){
        sub4::solve();
    }
    else{
        sub2567::solve();
    }
}

Compilation message (stderr)

fancyfence.cpp: In function 'int main()':
fancyfence.cpp:75:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   75 |         freopen(taskname".inp", "r", stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~

• 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