Submission #609297

#	Time	Username	Problem	Language	Result	Execution time	Memory
609297		1bin	Fancy Fence (CEOI20_fancyfence)	C++14	100 / 100	30 ms	4180 KiB

fancyfence

#include <bits/stdc++.h>

using namespace std;

#define all(v) v.begin(), v.end()
typedef long long ll;
const int NMAX = 1e5 + 5;
const ll mod = 1e9 + 7;
ll n, h[NMAX], w[NMAX], ans, x, ix, mxh, wd;
stack<int> st;

int main(void){
    ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);
    
    cin >> n;
    for(int i = 1; i <= n; i++) cin >> h[i];
    for(int i = 1; i <= n; i++) cin >> w[i], w[i] = (w[i] + w[i - 1]) % mod;
    st.emplace(0);
    for(int i = 1; i <= n; i++){
        while(st.size() >= 2 && h[st.top()] > h[i]){
            ix = st.top(); st.pop();
            mxh = max(h[st.top()], h[i]);
            wd = w[ix] - w[st.top()]; wd = (wd % mod + mod) % mod;
            ans += (h[ix] * (h[ix] + 1) / 2 - mxh * (mxh + 1) / 2) % mod * (wd * (wd + 1) / 2 % mod); ans %= mod;
            if(h[st.top()] > h[i]) w[st.top()] = w[ix];
        }
        if(h[st.top()] == h[i]) st.pop();
        st.emplace(i);
    }
    
    while(st.size() >= 2){
        ix = st.top(); st.pop();
        wd = w[n] - w[st.top()]; wd = (wd % mod + mod) % mod;
        ans += (h[ix] * (h[ix] + 1) / 2 - h[st.top()] * (h[st.top()] + 1) / 2) % mod * (wd * (wd + 1) / 2 % mod); ans %= mod;
    }
    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