Submission #982601

#	Time	Username	Problem	Language	Result	Execution time	Memory
982601		Mighilon	Fancy Fence (CEOI20_fancyfence)	C++17	100 / 100	25 ms	5592 KiB

fancyfence

#include <bits/stdc++.h>
using namespace std;
 
#ifdef DEBUG
#include "../Library/debug.h"
#else
#define dbg(x...)
// #define cin fin
// #define cout fout
// const string FILE_NAME = ""; ifstream fin(FILE_NAME + ".in"); ofstream fout(FILE_NAME + ".out");
#endif
 
typedef long long ll;
typedef long double ld;
typedef pair<int, int> pi;
typedef pair<ll, ll> pl;
typedef vector<int> vi;
typedef vector<ll> vl;
typedef vector<pi> vpi;
typedef vector<pl> vpl; 
 
#define FOR(i, a, b) for (int i = (a); i < (b); ++i)
#define F0R(i, a) for (int i = 0; i < (a); ++i)
#define FORd(i, a, b) for (int i = (b) - 1; i >= (a); --i)
#define F0Rd(i, a) for (int i = (a) - 1; i >= 0; --i)
#define trav(a, x) for (auto& a : x)
#define f first 
#define s second
#define pb push_back
#define sz(x) (int)(x).size()
#define all(x) x.begin(), x.end()
 
const char nl = '\n';
const int INF = 1e9;
const ll MOD = 1e9 + 7;
const int mxN = 1e6 + 1;


ll mul(ll a, ll b){
    return (ll) a * b % MOD;
}
const ll INV_TWO = (MOD + 1) / 2;
ll half(ll a){
    return mul(a, INV_TWO);
}

void add_self(ll& a, ll b){
    a += b;
    if(a >= MOD)
        a -= MOD;
    while(a < 0){
        a += MOD;
    }
}

ll f(ll a){
    return half(mul(a, a + 1));
}

void solve(){
    int n;
    cin >> n;
    vl h(n + 1), w(n + 1);
    F0R(i, n)
        cin >> h[i];
    F0R(i, n)
        cin >> w[i];
    h[n] = 0;
    w[n] = 0;
    // h, totalw;
    stack<array<ll, 2>> st;
    ll ans = 0;
    FOR(i, 0, n + 1){
        ll w_left = 0;
        while(!st.empty() && st.top()[0] >= h[i]){
            add_self(w_left, st.top()[1]);
            add_self(ans, mul(f(st.top()[0]), f(w_left)));
            add_self(ans, -mul(f(st.top()[0]), f(w_left - st.top()[1])));
            st.pop();
        }
        /* dbg(i, w_left, h[i], w[i]); */
        /* dbg(ans); */
        if(w_left != 0){
            add_self(ans, -mul(f(h[i]), f(w_left)));
        }
        /* dbg(ans); */
        st.push({h[i], (w[i] + w_left) % MOD});
    }
    cout << ans << nl;
}
 
int32_t main(){
    ios::sync_with_stdio(false); cin.tie(NULL); cout.tie(NULL);
    
    int TC = 1;
    /* cin >> TC; */
    while(TC--){
        solve();
    }
    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