倍杀测量者(差分约束)

Posted 2021-11-09 thusloop

倍杀测量者

//#pragma GCC optimize(2)
//#pragma GCC optimize(3,"Ofast","inline")
#include<bits/stdc++.h>
#define int long long
#define fi first
#define se second
#define pb push_back
#define pii pair<int,int>
#define ios ios::sync_with_stdio(false);cin.tie(0);cout.tie(0);
using namespace std;
const int inf=(int)8e18+100;
const int maxn=2e5+100;
int n,s,t;
double dis[maxn];
int num[maxn];
bool vis[maxn];
struct node
{
	int v,op;
	double w;
	double k;
};
vector<node>g[maxn];
bool spfa(double T)
{
	queue<int>q;
	for(int i=0;i<=n;i++)
	{
		dis[i]=inf;
		num[i]=0;
		vis[i]=0;
	}
	num[n+1]++;
	dis[n+1]=0;
	vis[n+1]=1;
	q.push(n+1);
	while(!q.empty())
	{
		int now=q.front();
		q.pop();
		vis[now]=0;
		for(auto it:g[now])
		{
			double w;
			if(it.op==0)w=it.w;
			if(it.op==1)w=-log2(it.k-T);
			if(it.op==2)w=log2(it.k+T);
			if(dis[now]+w<dis[it.v])
			{
				dis[it.v]=dis[now]+w;
				if(!vis[it.v])
				{
					vis[it.v]=1;
					q.push(it.v);
					num[it.v]++;
					if(num[it.v]>=n+1)return 0;
				}
			}
		}
	}
	return 1;
}
signed main()
{
	double l=0,r=10;
	cin>>n>>s>>t;
	for(int i=1;i<=s;i++)
	{
		int op,x,y;
		double k;
		cin>>op>>x>>y>>k;		
		g[x].pb({y,op,0,k});
		if(op==1)r=min(r,k);
	}
	for(int i=1;i<=t;i++)
	{
		int c;
		double x;
		cin>>c>>x;
		g[0].pb({c,0,log2(x),0});
		g[c].pb({0,0,-log2(x),0});
	}
	for(int i=0;i<=n;i++)
	{
		g[n+1].pb({i,0,0,0});
	}
	if(spfa(0))
	{
		cout<<"-1\\n";
		return 0;
	}
	while(r-l>1e-5)
	{
		double mid=(l+r)/2;
		if(spfa(mid))r=mid;
		else l=mid;
	}
	printf("%lf\\n",l);
}