Submission #667539

#	Time	Username	Problem	Language	Result	Execution time	Memory
667539		berr	Fancy Fence (CEOI20_fancyfence)	C++17	100 / 100	278 ms	7508 KiB

fancyfence

#include <bits/stdc++.h>
using namespace std;
#define int long long
const int N=1e5+37;
int p[N], vis[N], length[N];
int sum, ans=0, mod=1e9+7;


int s(int x, int y){
    return ((x+y)%mod+mod)%mod;
}

int mul(int x, int y){
    return (x*y)%mod;
}

int poww(int x, int y){
    if(y==0) return 1;

    int tmp=poww(x, y/2);

    if(y&1) return mul(tmp, mul(tmp, x));
    return mul(tmp, tmp);
}

int val(int x){
    return mul(mul(x, (x+1)), poww(2, mod-2));
}
int find(int x){
    return (p[x]!=x)?p[x]=find(p[x]):x;
}

void dsu(int x, int y){
    x=find(x);
    y=find(y);

    if(x==y) return;
    sum=s(sum, -val(length[x]));
    sum=s(sum, -val(length[y]));
    p[y]=x;
    length[x]=s(length[x], length[y]);
    sum=s(sum, val(length[x]));
}

signed main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(0);

    int n; cin>>n;

    vector<array<int, 3>> a(n+1);

    for(int i=1; i<=n; i++) p[i]=i;

    for(int i=0; i<n; i++){
        cin>>a[i][0];
        a[i][2]=i+1;
    }

    for(int i=0; i<n; i++){
        cin>>a[i][1];
        length[i+1]=a[i][1];
    }

    sort(a.begin(), a.end());

    reverse(a.begin(), a.end());


    for(int i=0; i<a.size()-1; i++)
    {
        int p=a[i][2], len=a[i][1], h=a[i][0];
        sum=s(sum, val(length[p])); vis[p]=1;

        if(vis[p-1]&&vis[p+1]){

            dsu(p, p-1);
            dsu(p, p+1);

        }
        else if(vis[p-1]){
            dsu(p, p-1);
        }
        else if(vis[p+1]){
            dsu(p, p+1);
        }
        ans=s(ans, mul(sum, s(val(h), -val(a[i+1][0]))));

    }

    cout<<ans; 

}

Compilation message (stderr)

fancyfence.cpp: In function 'int main()':
fancyfence.cpp:71:19: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::vector<std::array<long long int, 3> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   71 |     for(int i=0; i<a.size()-1; i++)
      |                  ~^~~~~~~~~~~
fancyfence.cpp:73:24: warning: unused variable 'len' [-Wunused-variable]
   73 |         int p=a[i][2], len=a[i][1], h=a[i][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