Submission #946246

#	Time	Username	Problem	Language	Result	Execution time	Memory
946246		PM1	LOSTIKS (INOI20_lostiks)	C++17	0 / 100	57 ms	41308 KiB

Main

#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define fr first
#define sc second
const int mxn=1e6+5,sz=(1<<20);
int n,dis[40][40],par[mxn][22],c[mxn],key[25],door[25],cnt=0,d[mxn];
ll dp[sz][25],ans=1e9;
vector<pair<int,int>>v[mxn];
void dfs(int z,int f=0){
	for(int i=1;i<=20;i++)
		par[z][i]=par[par[z][i-1]][i-1];
	for(auto i:v[z]){
		if(par[z][0]!=i.fr){
			par[i.fr][0]=z;
			c[i.fr]=c[z];
			d[i.fr]=d[z]+1;
			if(i.sc){
				door[++cnt]=z;
				key[cnt]=i.sc;
				c[i.fr]|=(1<<(cnt-1));
			}
			dfs(i.fr);
		}
	}
}
int lca(int x,int y){
	if(x==0 || y==0)return 0;
	if(d[x]<d[y])swap(x,y);
	int res=0;
	for(int i=20;i>=0;i--){
		if((1<<i)<=d[x]-d[y])x=par[x][i],res+=(1<<i);
	}
	if(x==y)return res;
	for(int i=20;i>=0;i--){
		if(par[x][i]!=par[y][i])x=par[x][i],y=par[y][i],res+=(1<<(i+1));
	}
	return res+2;
}
int main(){
	ios::sync_with_stdio(false);
	cin.tie(0);
	cout.tie(0);
	cin>>n;
	cin>>door[21]>>key[21];
	for(int i=1;i<n;i++){
		int x,y,w;
		cin>>x>>y>>w;
		v[x].push_back({y,w});
		v[y].push_back({x,w});
	}
	dfs(door[21]);
	for(int i=1;i<=21;i++){
		for(int j=1;j<=21;j++){
			dis[i][j]=lca(door[i],key[j]);
		}
	}
	for(int i=0;i<cnt;i++){
		if(!c[door[i+1]] && !c[key[i+1]])
			dp[(1<<i)][i]=dis[21][i+1]+dis[i+1][i+1];
		else
			dp[(1<<i)][i]=1e9;
		if(((1<<i)&(c[key[21]]))==c[key[21]])
			ans=min(ans,dp[(1<<i)][i]+dis[i+1][21]);
	}
	for(int i=2;i<(1<<cnt);i++){
		for(int j=0;j<cnt;j++){
			dp[i][j]=1e9;
			if((i&(1<<j)) && (i&c[door[j+1]])==c[door[j+1]] && (i&c[key[j+1]])==c[key[j+1]]) {
				for(int w=0;w<cnt;w++){
					if(i&(1<<w)){
						if(w!=j ){
							dp[i][j]=min(dp[i][j],dis[j+1][j+1]+dis[w+1][j+1]+dp[i-(1<<j)][w]);
							
						}
					}
				}
				if((i&(c[key[21]]))==c[key[21]]){
					ans=min(ans,dp[i][j]+dis[j+1][21]);
				}
			}
		}
	
	}
	if(c[key[21]]==0)ans=dis[21][21];
	assert(ans>=0);
	cout<<ans;
	return 0;
}

• Subtask 1: 0 / 23
• Subtask 2: 0 / 36
• Subtask 3: 0 / 41