Submission #100902

#	Time	Username	Problem	Language	Result	Execution time	Memory
100902		autumn_eel	Telegraph (JOI16_telegraph)	C++14	100 / 100	211 ms	23032 KiB

telegraph

#include <bits/stdc++.h>
#define rep(i,n)for(int i=0;i<(n);i++)
using namespace std;
typedef long long ll;
typedef pair<int,int>P;
 
vector<int>E[200000],G[200000];
int deg[200000];
int a[200000],c[200000];
bool loop[200000];
int id[200000];
int loopMax[200000],loopcnt[200000],loopsz[200000];
 
void dfs(int v,int k){
	id[v]=k;
	for(int u:E[v]){
		if(id[u]==-1){
			dfs(u,k);
		}
	}
}
ll ans=0;
 
void dfs2(int v){
	int Max=0;
	int Max2=0;
	for(int u:E[v]){
		if(loop[u]){
			Max2=c[u];
		}
		else{
			dfs2(u);
			Max=max(Max,c[u]);
		}
	}
	if(Max2>Max){
		loopMax[id[v]]=max(loopMax[id[v]],Max-Max2);
		loopcnt[id[v]]++;
	}
	ans+=max(Max,Max2);
}
 
 
int main(){
	int n;cin>>n;
	rep(i,n){
		scanf("%d%d",&a[i],&c[i]);a[i]--;
		deg[a[i]]++;deg[i]++;
		E[a[i]].push_back(i);
		G[a[i]].push_back(i);
		G[i].push_back(a[i]);
	}
	queue<int>que;
	rep(i,n){
		if(deg[i]==1){
			que.push(i);
		}
	}
	memset(loop,1,sizeof(loop));
	while(!que.empty()){
		int p=que.front();que.pop();
		loop[p]=false;
		for(int u:G[p]){
			if(deg[u]>1){
				deg[u]--;
				if(deg[u]==1){
					que.push(u);
				}
			}
		}
	}
	memset(id,-1,sizeof(id));
	int cnt=0;
	rep(i,n){
		if(loop[i]&&id[i]==-1){
			dfs(i,cnt++);
		}
	}
	bool ok=true;
	rep(i,n){
		if(!loop[i])ok=false;
	}
	if(ok&&cnt==1){
		puts("0");
		return 0;
	}
	rep(i,cnt)loopMax[i]=INT_MIN;
	rep(i,n){
		if(loop[i]){
			dfs2(i);
			loopsz[id[i]]++;
		}
	}
	rep(i,cnt){
		if(loopsz[i]&&loopsz[i]==loopcnt[i]){
			ans+=loopMax[i];
		}
	}
	ll ans2=0;
	rep(i,n)ans2+=c[i];
	cout<<ans2-ans<<endl;
}

Compilation message (stderr)

telegraph.cpp: In function 'int main()':
telegraph.cpp:47:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d%d",&a[i],&c[i]);a[i]--;
   ~~~~~^~~~~~~~~~~~~~~~~~~~

• Subtask 1: 10 / 10
• Subtask 2: 30 / 30
• Subtask 3: 30 / 30
• Subtask 4: 30 / 30