OJ-Problems-Source/HDOJ/1874.cpp

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2016-08-22 14:29:33 +08:00
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <algorithm>
using namespace std;
#define INF 0x3f3f3f3f
namespace SPFA
{
const int MAXN = 256;
int d[MAXN];/// distance [ From S to ... ]
int v[MAXN];/// visit
int q[MAXN];///
int mp[MAXN][MAXN]; /// mp[i][j] i<--> j is connected.
int n;
int spfa(int s,int t)
{
memset(d,0x3f,sizeof(d));
memset(v,0,sizeof(v));
/*
for(int i=1;i<MAXN;i++)
d[i]=INF,v[i]=0;*/
int cnt=0;
q[cnt++]=s;
v[s]=1;
d[s]=0;
while(cnt>0)
{
int c=q[--cnt];
v[c]=0;
for(int i=1;i<=n;i++)
{
if(mp[c][i]!=INF&&d[i]>d[c]+mp[c][i])
{
d[i]=d[c]+mp[c][i];
if(!v[i]) v[i]=1,q[cnt++]=i;
}
}
}
return d[t];
}
}/// End of NameSpace SPFA
int main()
{
using namespace SPFA;
int N,M;
while(scanf("%d %d",&N,&M)==2)
{
memset(mp,0x3f,sizeof(mp));
for(int i=0;i<M;i++)
{
int a,b,cost;
scanf("%d %d %d",&a,&b,&cost);
++a;++b;
if(mp[a][b]>cost)
{
mp[b][a]=mp[a][b]=cost;
}
}
int s,t;
scanf("%d %d",&s,&t);
if(s==t)
{
printf("0\n");continue;
}
++s;++t;
SPFA::n=N;
int ans=spfa(s,t);
printf("%d\n",ans>=INF ? -1 : ans );
}
return 0;
}