Submission #167652

#	Time	Username	Problem	Language	Result	Execution time	Memory
167652		HungAnhGoldIBO2020	Mag (COCI16_mag)	C++14	120 / 120	607 ms	173080 KiB

mag

#include<bits/stdc++.h>
using namespace std;
const int N=1e6+2;
const int inf=1e9+7;
vector<int> adj[N];
int val[N],f[N],max1=1;
pair<int,int> nei[N],nei1[N];
void dfs1(int x,int p,int mx){
	for(int i:adj[x]){
		if(i!=p){
			if(val[x]==1){
				int val=-1;
				if(i!=nei[x].second){
					val=nei[x].first+1;
				}
				else{
					val=nei1[x].first+1;
				}
				dfs1(i,x,max(mx+1,val));
			}
			else{
				dfs1(i,x,0);
			}
		}
	}
//	cout<<x<<' '<<nei[x].first<<' '<<nei[x].second<<' '<<mx<<' '<<nei1[x].first<<' '<<nei1[x].second<<endl;
	if(val[x]==2&&nei[x].first==max1&&(nei1[x].first==max1||mx==max1)){
		cout<<2<<'/'<<2*max1+1;
		exit(0);
	}
}
void dfs(int x,int p){
	int mx=0;
	if(val[x]==1){
		f[x]=1;
	}
	for(int i:adj[x]){
		if(i!=p){
			dfs(i,x);
			if(nei[x].first<=f[i]){
				nei1[x]=nei[x];
				nei[x]={f[i],i};
			}
			else{
				if(nei1[x].first<f[i]){
					nei1[x]={f[i],i};
				}
			}
			if(val[i]>1||val[x]>1){
				continue;
			}
			if(f[x]<=f[i]+1){
				mx=f[x];
				f[x]=f[i]+1;
			}
			else{
				if(f[i]+1>mx){
					mx=f[i]+1;
				}
			}
		}
	}
	max1=max(max1,mx+f[x]-1);
}
signed main(){
	ios::sync_with_stdio(0);
	cin.tie(0);
	int n,i,j,k,l,min1=inf;
	cin>>n;
	for(i=1;i<n;i++){
		cin>>j>>k;
		adj[j].push_back(k);
		adj[k].push_back(j);
	}
	for(i=1;i<=n;i++){
		cin>>val[i];
		min1=min(min1,val[i]);
	}
	if(min1>1){
		cout<<min1<<'/'<<1;
		return 0;
	}
	dfs(1,1);
//	for(i=1;i<=n;i++){
//		cout<<i<<' '<<f[i]<<endl;
//	}
	dfs1(1,1,0);
	cout<<1<<'/'<<max1;
	
}
/*
5
1 2
2 4
1 3
5 2
2
1
1
1
3 
*/
/*
5
1 2 
2 3
3 4
4 5
1 1 2 1 1
*/

Compilation message (stderr)

mag.cpp: In function 'int main()':
mag.cpp:68:14: warning: unused variable 'l' [-Wunused-variable]
  int n,i,j,k,l,min1=inf;
              ^

• Subtask 1: 12 / 12
• Subtask 2: 12 / 12
• Subtask 3: 12 / 12
• Subtask 4: 12 / 12
• Subtask 5: 12 / 12
• Subtask 6: 12 / 12
• Subtask 7: 12 / 12
• Subtask 8: 12 / 12
• Subtask 9: 12 / 12
• Subtask 10: 12 / 12