Submission #478176

#	Time	Username	Problem	Language	Result	Execution time	Memory
478176		starplat	Islands (IOI08_islands)	C++14	9 / 100	340 ms	49848 KiB

islands

#include <bits/stdc++.h>
#define int long long
using namespace std;
int n,v,w,vis[100005],path,ans,ct;
pair<int,int> dist[100005];
struct vertex{
	int x,dw,rw;//dw is the discretized weight, rw is the original weight
};
vector<vertex> g[100005];
map<int,int> dis;
vector<int> clr,edge;
priority_queue<pair<int,int>> q;
void dij(int oof)
{
	q.push({0,oof});
	dist[oof].first=0;
	while (q.size()){
		v=q.top().second;
		q.pop();
		if (vis[v]) continue;
		vis[v]=1;
		//cout<<v<<"\n";
		clr.push_back(v);
		for (auto i:g[v]){
			if (dist[i.x].first>dist[v].first+i.dw){
			//	cout<<i.x<<"\n";
				dist[i.x].first=dist[v].first+i.dw;
				dist[i.x].second=dist[v].second+i.rw;
				q.push({dist[i.x].first,i.x});
			}
		}
	}
}
signed main()
{
	cin>>n;
	for (int i=1;i<=n;i++){
		cin>>v>>w;
		g[i].push_back((vertex){v,0,w});
		g[v].push_back((vertex){i,0,w});
		edge.push_back(w);
	}
	sort(edge.begin(),edge.end());
	reverse(edge.begin(),edge.end());
	for (int i:edge) if (!dis[i]) dis[i]=++ct;
	for (int i=1;i<=n;i++){
		for (int j=0;j<g[i].size();j++){
			g[i][j].dw=dis[g[i][j].rw];
		}
	}
	for (int i=1;i<=n;i++) dist[i].first=1e18;
	for (int i=1;i<=n;i++){
		if (!vis[i]) {
			dij(i);
			int mx=0,node=0;
			for (int i:clr) {
				if (dist[i].second>mx) mx=dist[i].second,node=i;
				vis[i]=0,dist[i]={1e18,0};
			}
			
			path=0;
			dij(node);
			for (int i:clr) path=max(path,dist[i].second);
			clr.clear();
			ans+=path;
		//	cout<<path<<"\n";
		}
	}
	cout<<ans<<"\n";
}
//for each connected component find the tree diameter,and travel to next subgraph?
//dijstra with longest path?no good, there is nothing call longest dijstra...
//love to do graph questions, at the same time hate don't no how to solve graph questions..
//sort the edges by non-increasing order, and distrecitze the edges by weight from small to large

Compilation message (stderr)

islands.cpp: In function 'int main()':
islands.cpp:47:17: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::vector<vertex>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   47 |   for (int j=0;j<g[i].size();j++){
      |                ~^~~~~~~~~~~~

• Subtask 1: 9 / 33
• Subtask 2: 0 / 3
• Subtask 3: 0 / 4
• Subtask 4: 0 / 10
• Subtask 5: 0 / 10
• Subtask 6: 0 / 10
• Subtask 7: 0 / 10
• Subtask 8: 0 / 10
• Subtask 9: 0 / 10