次短路删边法

#include<bits/stdc++.h>
using namespace std;
const int N = 210,INF = 0x3f3f3f3f;
using pr = pair<int,double>;
using pr2 = pair<double,int>;
int n,m;
pair<int,int> node[N];
vector<pr> g[N];
 
double dist[N];
int st[N];
priority_queue<pr2,vector<pr2>,greater<pr2>> q;
int pre[N];

// 距离函数
double d(int u,int v)
{
	return sqrt((node[u].first-node[v].first)*(node[u].first-node[v].first)+(node[u].second-node[v].second)*(node[u].second-node[v].second));
}

void dijkstra(int e1,int e2)
{		
	for(int i=1;i<=n;i++)
	{
		dist[i]=INF;
	}
	memset(st,0,sizeof st);
	dist[1] = 0;
	q.push({0,1});  
	while(q.size())
	{
		int t = q.top().second;
		q.pop();
		if(st[t] == 1)
			continue;
		st[t] = 1;
		for(int i=0;i<g[t].size();i++)
		{
			int j = g[t][i].first;
			double w = g[t][i].second;
			// 删边
			if(t==e1 && j==e2 || t==e2 && j==e1)
				continue;
			if(dist[j] > dist[t]+w)  
			{	 
				dist[j] = dist[t]+w;
				q.push({dist[j],j});
				if(e1==-1 && e2==-1)
					pre[j] = t;
			}
		}
	}
}

int main()
{	
	cin>>n>>m;
	for(int i=1;i<=n;i++)
	{
		cin>>node[i].first>>node[i].second;
	}
	for(int i=1;i<=m;i++)
	{
		int u,v;
		cin>>u>>v;
		double w = d(u,v);
		g[u].push_back({v,w});
		g[v].push_back({u,w});
	}
	
	dijkstra(-1,-1); 
	
	double ans = INF;
	for(int i=n;i!=1;i=pre[i])
	{
		dijkstra(pre[i],i);
		ans = min(ans,dist[n]);
	}
	
	if(ans == INF)
		cout<<-1;
	else
		printf("%.2f",ans);
	return 0;
}