Submission #1082498

#	Time	Username	Problem	Language	Result	Execution time	Memory
1082498		steveonalex	Fancy Fence (CEOI20_fancyfence)	C++17	100 / 100	63 ms	10452 KiB

fancyfence

#include <bits/stdc++.h>
 
using namespace std;
 
typedef long long ll;
typedef unsigned long long ull;
 
#define MASK(i) (1LL << (i))
#define GETBIT(mask, i) (((mask) >> (i)) & 1)
#define ALL(v) (v).begin(), (v).end()
#define block_of_code if(true)
 
ll max(ll a, ll b){return (a > b) ? a : b;}
ll min(ll a, ll b){return (a < b) ? a : b;}
ll gcd(ll a, ll b){return __gcd(a, b);}
ll lcm(ll a, ll b){return a / gcd(a, b) * b;}
 
ll LASTBIT(ll mask){return (mask) & (-mask);}
int pop_cnt(ll mask){return __builtin_popcountll(mask);}
int ctz(ull mask){return __builtin_ctzll(mask);}
int logOf(ull mask){return 63 - __builtin_clzll(mask);}
 
mt19937_64 rng(chrono::high_resolution_clock::now().time_since_epoch().count());
ll rngesus(ll l, ll r){return l + (ull) rng() % (r - l + 1);}
double rngesus_d(double l, double r){
    double cur = rngesus(0, MASK(60) - 1);
    cur /= MASK(60) - 1;
    return l + cur * (r - l);
}
 
template <class T1, class T2>
    bool maximize(T1 &a, T2 b){
        if (a < b) {a = b; return true;}
        return false;
    }
 
template <class T1, class T2>
    bool minimize(T1 &a, T2 b){
        if (a > b) {a = b; return true;}
        return false;
    }
 
template <class T>
    void printArr(T container, string separator = " ", string finish = "\n", ostream &out = cout){
        for(auto item: container) out << item << separator;
        out << finish;
    }
 
template <class T>
    void remove_dup(vector<T> &a){
        sort(ALL(a));
        a.resize(unique(ALL(a)) - a.begin());
    }


 
const int MOD = 1e9 + 7;
struct Modular{
    ll x;
    Modular(ll _x = 0){x = _x;}
    Modular& operator += (Modular y){
        x += y.x;
        if (x >= MOD) x -= MOD;
        return *this;
    }
    Modular operator + (Modular y) {
        Modular tmp = *this;
        return tmp += y;
    }
 
    Modular& operator -= (Modular y){
        x -= y.x;
        if (x < 0) x += MOD;
        return *this;
    }
    Modular operator - (Modular y) {
        Modular tmp = *this;
        return tmp -= y;
    }
 
    Modular& operator *= (Modular y){
        x *= y.x;
        if (x >= MOD) x %= MOD;
        return *this;
    }
    Modular operator * (Modular y) {
        Modular tmp = *this;
        return tmp *= y;
    }
 
    // use at your own risk
    bool operator == (Modular y){
        return x == y.x;
    }
    bool operator != (Modular y){
        return x != y.x;
    }
};
ostream& operator << (ostream& out, Modular x){
    out << x.x;
    return out;
}

const Modular half = 500000004;

struct DSU{
    int n;
    vector<int> parent, sz;
    vector<Modular> sum;
    Modular ans;

    DSU(int _n){
        n = _n;
        parent.resize(n); sz.resize(n, 1);
        sum.resize(n);
        for(int i = 1; i<n; ++i) parent[i] = i;
    }

    void set_sum(int x, ll y){
        sum[x] = y;
        ans += sum[x] * (sum[x] + 1) * half;
    }

    int find_set(int u){return (u == parent[u]) ? u : (parent[u] = find_set(parent[u]));}
    bool same_set(int u, int v){return find_set(u) == find_set(v);}

    bool join_set(int u, int v){
        u = find_set(u), v = find_set(v);
        if (u != v){
            ans -= (sum[u] * (sum[u] + 1) + sum[v] * (sum[v] + 1)) * half;
            if (sz[u] < sz[v]) swap(u, v);
            parent[v] = u;
            sz[u] += sz[v];
            sum[u] += sum[v];
            ans += sum[u] * (sum[u] + 1) * half;
            return true;
        }
        return false;
    }

    Modular get_ans(){return ans;}
};

int main(void){
    ios::sync_with_stdio(0);cin.tie(0); cout.tie(0);
    clock_t start = clock();

    int n; cin >> n;
    vector<pair<int,int>> a(n);
    for(int i= 0; i<n; ++i) cin >> a[i].first;
    for(int i= 0; i<n; ++i) cin >> a[i].second;

    vector<int> b;
    for(int i= 0; i<n; ++i) b.push_back(a[i].first);

    b.push_back(0);
    remove_dup(b);
    
    vector<vector<int>> sigma(b.size());
    for(int i = 0; i<n; ++i){
        int idx = lower_bound(ALL(b), a[i].first) - b.begin();
        sigma[idx].push_back(i);
    }

    DSU mst(n);
    vector<bool> activated(n);

    Modular ans;
    for(int i = b.size() - 1; i>=1; --i){
        for(int j: sigma[i]){
            mst.set_sum(j, a[j].second);
            activated[j] = true;
            if (j - 1 >= 0 && activated[j-1]) mst.join_set(j, j-1);
            if (j + 1 < n && activated[j+1]) mst.join_set(j, j+1);
        }
        Modular x = b[i] - b[i-1], y = b[i-1];
        Modular z = mst.get_ans();
        ans += z * (x * (x+1) * half + x * y);
    }
    cout << ans << "\n";


    cerr << "Time elapsed: " << clock() - start << " ms\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: 18 / 18
• Subtask 7: 27 / 27