Submission #944843

#	Time	Username	Problem	Language	Result	Execution time	Memory
944843		dsyz	Fancy Fence (CEOI20_fancyfence)	C++17	12 / 100	2 ms	2396 KiB

fancyfence

#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ld = long double;
#define MAXN (1000005)
ld ans = 0, cursum = 0, mod = 1e9 + 7;
ll parent[MAXN], SIZE[MAXN];
ld tri(ld h){
	return ((h + 1) * h) / ld(2); //the triangle sum formula is N*(N + 1) / 2 (basically the sum of 1,2,...,N)
}
ll find_set(ll x){
	if(parent[x] == x) return x;
	parent[x] = find_set(parent[x]);
	return parent[x];
}
bool same_set(ll x,ll y){
	return find_set(x) == find_set(y);
}
void merge_set(ll x,ll y){
	if(same_set(x,y)) return;
	ll Xsize = SIZE[find_set(x)], Ysize = SIZE[find_set(y)];
	/*cursum -= (((Xsize + 1) * Xsize) / 2);
	cursum -= (((Ysize + 1) * Ysize) / 2);
	cursum = (cursum + mod) % mod;
	ll totalsize = Xsize + Ysize;
	cursum += (((totalsize + 1) * totalsize) / 2);
	cursum = (cursum + mod) % mod;*/
	cursum += (Xsize * Ysize);
	cursum = fmod(cursum + mod,mod);
	ll totalsize = Xsize + Ysize;
	parent[find_set(x)] = find_set(y);
	SIZE[find_set(x)] = totalsize;
}
int main() {
	ios_base::sync_with_stdio(false);cin.tie(0);
	ll N;
	cin>>N;
	pair<pair<ll,ll>,ll> arr[N];
	for(ll i = 0;i < N;i++){
		cin>>arr[i].first.first; //H[i]
	}
	for(ll i = 0;i < N;i++){
		cin>>arr[i].first.second; //W[i]
	}
	for(ll i = 0;i < N;i++){
		arr[i].second = i;
		parent[i] = i;
		SIZE[i] = arr[i].first.second;
	}
	set<ll,greater<ll> > heights;
	for(ll i = 0;i < N;i++){
		heights.insert(arr[i].first.first);
	}
	sort(arr,arr + N,greater<pair<pair<ll,ll>,ll> >());
	bool can[N];
	memset(can,0,sizeof(can));
	ll ptr = -1;
	for(auto h : heights){
		cursum = 0;
		while(ptr + 1 < N && arr[ptr + 1].first.first == h){
			ptr++;
			ll ind = arr[ptr].second;
			can[ind] = 1;
			cursum += (((arr[ptr].first.second + 1) * arr[ptr].first.second) / 2);
			cursum = fmod(cursum + mod,mod);
			if(ind >= 1 && can[ind - 1]){
				//cout<<"MERGED: "<<ind - 1<<" "<<ind<<'\n';
				merge_set(ind - 1,ind);
			}
			cursum = fmod(cursum + mod,mod);
			if(ind < N - 1 && can[ind + 1]){
				//cout<<"MERGED: "<<ind<<" "<<ind + 1<<'\n';
				merge_set(ind,ind + 1);
			}
			cursum = fmod(cursum + mod,mod);
		}
		//cout<<"HEIGHT = "<<h<<" have cursum of "<<cursum<<'\n';
		ans += (fmod(cursum + mod,mod) * fmod(tri(h),mod));
		ans = fmod(ans + mod,mod);
	}
	cout<<fmod(ans + mod,mod)<<'\n';
}

/*
2
2 2
1 2
*/

• Subtask 1: 0 / 0
• Subtask 2: 12 / 12
• Subtask 3: 0 / 13
• Subtask 4: 0 / 15
• Subtask 5: 0 / 15
• Subtask 6: 0 / 18
• Subtask 7: 0 / 27