Submission #1059123

#	Time	Username	Problem	Language	Result	Execution time	Memory
1059123		DucNguyen2007	Fancy Fence (CEOI20_fancyfence)	C++14	100 / 100	26 ms	5980 KiB

fancyfence

#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define ld long double
#define pii pair<int,int>
#define pll pair<ll,ll>
#define fi first
#define se second
const int maxN=1e5+5,MOD=1e9+7,REVMOD=250000002;
const ll inf=2e18;
int n,l[maxN+1],r[maxN+1];
ll h[maxN+1],w[maxN+1],s[maxN+1];
stack<int> st;
void clr()
{
    while(!st.empty())
    {
        st.pop();
    }
}
ll mul(ll x,ll y)
{
    return (x*y)%MOD;
}
ll sc(ll x1,ll x2)
{
    ll tmp=mul(x1+1,x2+1);
    tmp--;
    if(tmp<0)
    {
        tmp+=MOD;
    }
    return tmp;
}
ll calc(ll n,ll m)
{
    return mul(mul(mul(1LL*n,1LL*(n+1)),mul(1LL*m,1LL*(m+1))),REVMOD);
}
ll get(ll x1,ll x2,int i)
{
    return mul((mul(w[i]-1,x1+x2)+sc(x1,x2))%MOD,calc(1,h[i]));
}
int main()
{
    //freopen("","r",stdin);
    //freopen("","w",stdout);
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    cin>>n;
    for(int i=1;i<=n;i++)
    {
        cin>>h[i];
    }
    s[0]=0;
    for(int i=1;i<=n;i++)
    {
        cin>>w[i];
        s[i]=(s[i-1]+w[i])%MOD;
    }
    clr();
    for(int i=1;i<=n;i++)
    {
        while(!st.empty()&&h[st.top()]>=h[i])
        {
            st.pop();
        }
        if(st.empty())
        {
            l[i]=1;
        }
        else l[i]=st.top()+1;
        st.push(i);
    }
    clr();
    for(int i=n;i>=1;i--)
    {
        while(!st.empty()&&h[st.top()]>h[i])
        {
            st.pop();
        }
        if(st.empty())
        {
            r[i]=n;
        }
        else r[i]=st.top()-1;
        st.push(i);
    }
    ll ans=0;
    for(int i=1;i<=n;i++)
    {
        ll tmp1=s[i-1]-s[l[i]-1],tmp2=s[r[i]]-s[i];
        ans=(ans+get(tmp1,tmp2,i))%MOD;
        ans=(ans+calc(h[i],w[i]))%MOD;
        //cout<<i<<" "<<l[i]<<" "<<r[i]<<" "<<tmp1<<" "<<tmp2<<" "<<get(tmp1,tmp2,i)<<'\n';
    }
    cout<<ans;
}
/*5
5 9 49 32 4
1 1 1 1 1
*/

• 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