Submission #902701

#	Time	Username	Problem	Language	Result	Execution time	Memory
902701		KN200711	Fancy Fence (CEOI20_fancyfence)	C++14	100 / 100	49 ms	5948 KiB

fancyfence

# include <bits/stdc++.h>
# define ll long long
# define ld long double
# define fi first
# define se second
# define pll pair<ll, ll>
# define pdd pair<ld, ld>
# define pii pair<int, int>
using namespace std;

const ll MOD = 1e9 + 7;
int par[100001];
ll sz[100001], ans[100001];
ll C2(int a) {
  ll v = a * (a + 1ll) / 2ll;
  v %= MOD;
  return v;
}

int find(int a) {	
  if(a == par[a]) return a;	
  par[a] = find(par[a]);	
  return par[a];
}

void merge(int a, int b, ll c) {	
  a = find(a);	
  b = find(b);	
  if(a == b) return;	
  ans[a] += ans[b];	
  ans[a] %= MOD;	
	ll G = C2(c) * (C2(sz[a]) + C2(sz[b]));
	G %= MOD;
	
	par[b] = a;
	sz[a] += sz[b];
	sz[a] %= MOD;
	ans[a] -= G;
	ans[a] %= MOD;
	
	G = C2(c) * (C2(sz[a]));
	G %= MOD;
	
	ans[a] += G;
	ans[a] %= MOD;
}
 
bool vis[100001];
 
int main() {
	int N;
	scanf("%d", &N);
	vector<pair<pii, int> > arr(N);
	for(int i=0;i<N;i++) {
		par[i] = i;
		scanf("%d", &arr[i].fi.fi);
	}
	for(int i=0;i<N;i++) {
		scanf("%d", &arr[i].fi.se);
		ans[i] = C2(arr[i].fi.fi) * C2(arr[i].fi.se);
		sz[i] = arr[i].fi.se;
		ans[i] %= MOD;
		arr[i].se = i;
	}
	sort(arr.begin(), arr.end());
	for(int i=N-1;i>=0;i--) {
		int idx = arr[i].se;
		vis[idx] = 1;
		if(idx > 0 && vis[idx - 1]) merge(idx - 1, idx, arr[i].fi.fi);
		if(idx + 1 < N && vis[idx + 1]) merge(idx + 1, idx, arr[i].fi.fi);
	}
	if(ans[find(0)] < 0) ans[find(0)] += MOD;
	printf("%lld\n", ans[find(0)]);
}

Compilation message (stderr)

fancyfence.cpp: In function 'int main()':
fancyfence.cpp:52:7: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   52 |  scanf("%d", &N);
      |  ~~~~~^~~~~~~~~~
fancyfence.cpp:56:8: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   56 |   scanf("%d", &arr[i].fi.fi);
      |   ~~~~~^~~~~~~~~~~~~~~~~~~~~
fancyfence.cpp:59:8: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   59 |   scanf("%d", &arr[i].fi.se);
      |   ~~~~~^~~~~~~~~~~~~~~~~~~~~

• 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