[kuangbin带你飞]专题四 最短路练习

#include<iostream>
#include<cstring>
#include<algorithm>
#include<iomanip>
#include<cmath>
#include<cstdio>
#include<vector>
#include<string>
#include<map>
#include<queue>
#include<vector>
using namespace std;
/*
单源最短路 路径方向与switch方向同向那么路径权值0，否则为1
*/
#define MAXN 101
#define INF 0x3f3f3f3f
bool g[MAXN][MAXN],TO[MAXN][MAXN],been[MAXN];
int lowcost[MAXN],A,B,N;
int Dijkstra(int beg,int to)
{
for(int i=1;i<=N;i++)
{
lowcost[i] = INF;
been[i] = false;
}
lowcost[beg] = 0;
for(int i=0;i<N;i++)
{
int Minc = INF,k = -1;
for(int j=1;j<=N;j++)
{
if(!been[j]&&lowcost[j]<Minc)
{
Minc = lowcost[j];
k = j;
}
}
if(k==-1) break;
been[k] = true;
for(int j=1;j<=N;j++)
{
int cost;
if(!g[k][j]) cost = INF;
else
{
if(TO[k][j]==true)
cost = 0;
else cost = 1;
}
if(!been[j]&&lowcost[j]>lowcost[k]+cost)
{
lowcost[j] = lowcost[k]+cost;
}
}
}
return lowcost[to];
}
int main()
{
cin>>N>>A>>B;
int k,tmp;
for(int i=1;i<=N;i++)
{
cin>>k;
for(int j=1;j<=k;j++)
{
cin>>tmp;
if(j==1)
TO[i][tmp] = true;
g[i][tmp] = true;
}
}
int ans = Dijkstra(A,B);
if(ans!=INF)
cout<<ans<<endl;
else
cout<<-1<<endl;
return 0;
}