P1339 [USACO09OCT]Heat Wave
题目思路:这道题直接套SPFA就行了,什么都不用注意
code:
#include<cstring>
#include<cmath>
#include<cstdio>
#include<iostream>
using namespace std;
struct node
{
int x,y,z,next;
} a[1240010];
int hd[6210],s=0,q[2510],f[2510],minn[2510];
void add(int u,int v,int w)
{
a[++s].x=u;
a[s].y=v;
a[s].z=w;
a[s].next=hd[u];
hd[u]=s;
}
void spfa(int s)
{
q[1]=s;f[s]=1,minn[s]=0;
int h=0,t=1;
while(h<=t)
{
h++;
int tx=q[h];
for(int i=hd[tx];i;i=a[i].next)
{
if(minn[a[i].y]>minn[tx]+a[i].z)
{
minn[a[i].y]=minn[tx]+a[i].z;
if(f[a[i].y]==0)
{
t++;
f[tx]=1;
q[t]=a[i].y;
}
}
}
f[tx]=0;
}
}
int main()
{
memset(minn,127/3,sizeof(minn));
int n,m,s,t;
cin>>n>>m>>s>>t;
for (int i=1;i<=m;i++)
{
int u,c,w;
cin>>u>>c>>w;
add(u,c,w);
add(c,u,w);
}
spfa(min(s,t));
cout<<minn[max(s,t)]<<endl;
return 0;
}