51nod-1649-齐头并进

从1到n要么有条铁路要么是公路，所以若1->n是铁路那么dij公路即可，反之亦然

#include <iostream>
#include <cstdio>
#include <vector>
#include <queue>
#include <cstring>
using namespace std;
struct HeapNode
{
int u,d;
bool operator < (const HeapNode& rhs)const
{
return d>rhs.d;
}
};
const int INF=1e9;
bool line[410][410],done[410];
int d[410],n;
void dijkstra(bool flag);
int main()
{
int m,num1,num2;
scanf("%d%d",&n,&m);
for(int i=1;i<=m;i++)
{
scanf("%d%d",&num1,&num2);
line[num1][num2]=line[num2][num1]=true;
}
if(line[1]
)
dijkstra(false);
else
dijkstra(true);
if(d
==INF)
printf("-1\n");
else
printf("%d\n",d
);
return 0;
}
void dijkstra(bool flag)
{
memset(done,0,sizeof(done));
for(int i=1;i<=n;i++)
d[i]=INF;
d[1]=0;
priority_queue<HeapNode> last;
last.push(HeapNode{1,0});
while(!last.empty())
{
HeapNode now=last.top();
last.pop();
if(done[now.u])
continue;
done[now.u]=true;
for(int i=1;i<=n;i++)
{
if(line[now.u][i]==flag)
{
if(d[now.u]+1<d[i])
{
d[i]=d[now.u]+1;
last.push(HeapNode{i,d[i]});
}
}
}
}
}