Submission #882930

#	Time	Username	Problem	Language	Result	Execution time	Memory
882930		hamidh100	Fancy Fence (CEOI20_fancyfence)	C++17	100 / 100	23 ms	7432 KiB

fancyfence

/* In the name of God */

#include <bits/stdc++.h>

using namespace std;

typedef long long ll;
typedef long double ld;
typedef pair<int, int> PII;
typedef pair<ll, ll> PLL;
typedef vector<int> VI;
typedef vector<ll> VL;
#define PB push_back
#define MP make_pair
#define all(a) (a).begin(), (a).end()
#define endl '\n'
#define dbg(x) cerr << '[' << #x << ": " << x << "]\n"
#define dbg2(x, y) cerr << '[' << #x << ": " << x << ", " << #y << ": " << y << "]\n"
#define YES cout << "YES\n"
#define NO cout << "NO\n"

const ll INF = (ll)2e18 + 1386;
const ld EPS = 0.000000000000001;
const int MOD = 1e9 + 7;

inline int _add(int a, int b){ int res = a + b; return (res >= MOD ? res - MOD : res); }
inline int _neg(int a, int b){ int res = (abs(a - b) < MOD ? a - b : (a - b) % MOD); return (res < 0 ? res + MOD : res); }
inline int _mlt(ll a, ll b){ return (a * b % MOD); }
inline void fileIO(string i, string o){ freopen(i.c_str(), "r", stdin); freopen(o.c_str(), "w", stdout); }

const int MAXN = 2e5 + 5, inv2 = (MOD + 1) / 2;

int C(int x){ return _mlt(_mlt(x, x - 1), inv2); }

int h[MAXN], w[MAXN];
int lef[MAXN], rig[MAXN];
ll ps[MAXN];

int main(){
    ios_base::sync_with_stdio(0); cin.tie(0);
    int n;
    cin >> n;
    for (int i = 1; i <= n; i++) cin >> h[i];
    for (int i = 1; i <= n; i++){
        cin >> w[i];
        ps[i] = _add(ps[i - 1], w[i]);
    }
    int ans = 0;
    VI agha;
    for (int i = 1; i <= n; i++){
        while (!agha.empty() && h[agha.back()] > h[i]){
            agha.pop_back();
        }
        lef[i] = (agha.empty() ? 0 : agha.back());
        agha.PB(i);
    }
    agha.clear();
    for (int i = n; i >= 1; i--){
        while (!agha.empty() && h[agha.back()] >= h[i]){
            agha.pop_back();
        }
        rig[i] = (agha.empty() ? n + 1 : agha.back());
        agha.PB(i);
    }
    for (int i = 1; i <= n; i++){
        int l = lef[i] + 1, r = rig[i] - 1;
        int cw = _neg(C(_neg(ps[r], ps[l - 1]) + 1), _add(C(_neg(ps[i - 1], ps[l - 1]) + 1), C(_neg(ps[r], ps[i]) + 1)));
        int ch = C(h[i] + 1);
        ans = _add(ans, _mlt(cw, ch));
    }
    cout << ans;
    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