Submission #768829

#	Time	Username	Problem	Language	Result	Execution time	Memory
768829		LeoChen112358	Robot (JOI21_ho_t4)	C++14	100 / 100	841 ms	81736 KiB

Main

#include <bits/stdc++.h>
using namespace std;

const int Nlim=1e5,Mlim=2e5,Vlim=1e9;
const long INF=(long)Vlim*Mlim+1;
#define pii pair<long,pair<int,int>>
int N,M;
struct edge{
	int node,color,price;
	edge(int nn,int cc,int pp){
		node=nn;
		color=cc;
		price=pp;
	}
};
map<int,vector<edge>>conn[Nlim];
//cost = min(recolor you, recolor neighbors)
//cost to get to i
long dp1[Nlim];
//cost to get to i with a c-edge and will go thru another c-edge (so we'll recolor later)
//applies only when we are to recolor neighbors originally (gets affected)
map<int,long>dp2[Nlim],sum[Nlim];

int main(){
	ios::sync_with_stdio(0);
	cin.tie(0),cout.tie(0);
	cin>>N>>M;
	for(int i=0; i<M; i++){
		int a,b,c,p;
		cin>>a>>b>>c>>p;
		a--,b--,c--;
		conn[a][c].push_back(edge(b,c,p));
		conn[b][c].push_back(edge(a,c,p));//undirected
		sum[a][c]+=p;
		sum[b][c]+=p;
	}
	for(int i=0; i<N; i++)
		dp1[i]=INF;
	priority_queue<pii,vector<pii>,greater<pii>>PQ;
	PQ.push({0,{0,-1}});//cost,node,color
	dp1[0]=0;
	while(!PQ.empty()){
		long prc=PQ.top().first,node=PQ.top().second.first,col=PQ.top().second.second;
		PQ.pop();
		if(col==-1){//no need to recolor neighbor stuff (normal way)
			if(dp1[node]!=prc)continue;
			for(auto stuff:conn[node]){//each color
				for(auto i:stuff.second){
					//1. recolor this edge
					long v1=prc+i.price;
					if(v1<dp1[i.node]){
						dp1[i.node]=v1;
						PQ.push({dp1[i.node],{i.node,-1}});
					}
					//2. recolor neighbors
					long v2=prc+sum[node][i.color]-i.price;
					if(v2<dp1[i.node]){
						dp1[i.node]=v2;
						PQ.push({dp1[i.node],{i.node,-1}});
					}
					//3. recolor at next step (virtual transition)
					if(dp2[i.node].count(i.color)==0 or prc<dp2[i.node][i.color]){
						dp2[i.node][i.color]=prc;
						PQ.push({prc,{i.node,i.color}});
					}
				}
			}
		}
		else{//need to recolor neighbor stuff (special case)
			if(dp2[node][col]!=prc)continue;
			for(auto i:conn[node][col]){
				long val=sum[node][col];
				if(prc+val-i.price<dp1[i.node]){
					dp1[i.node]=prc+val-i.price;
					PQ.push({dp1[i.node],{i.node,-1}});
				}
			}
		}
	}
	if(dp1[N-1]==INF)cout<<-1<<'\n';
	else cout<<dp1[N-1]<<'\n';
}

• Subtask 1: 34 / 34
• Subtask 2: 24 / 24
• Subtask 3: 42 / 42