1752: [Usaco2005 qua]Til the Cows Come Home (SPFA)

#include<iostream>
#include<cstring>
#include<cstdio>
#define inf 0x7fffffff
using namespace std;
inline int read(){
int x=0,f=1;char ch=getchar();
while(ch<'0'||ch>'9'){if(ch=='-')f=-1;ch=getchar();}
while(ch>='0'&&ch<='9'){x=x*10+ch-'0';ch=getchar();}
return x*f;
}
struct edge{
int to,next,v;
}e[40001];
int n,m,cnt,head[10001],dis[10001];
void ins(int u,int v,int w){
e[++cnt]=(edge){v,head[u],w};head[u]=cnt;
e[++cnt]=(edge){u,head[v],w};head[v]=cnt;
}
void spfa() {
int q[10001], t = 0, w = 0;
bool inq[10001];
memset(inq, 0, sizeof (inq));
memset(dis, 127, sizeof (dis));
dis[1]=0;q[0]=1;inq[1]=1;
while (t <= w) {
int now = q[t++];
for (int i = head[now]; i; i = e[i].next) {
if (dis[now] + e[i].v < dis[e[i].to]) {
dis[e[i].to] = dis[now] + e[i].v;
if (!inq[e[i].to]) {
q[++w] = e[i].to;
inq[e[i].to] = 1;
}
}
}
inq[now] = 0;
}
}
int main(){
m=read();n=read();
for(int i=1;i<=m;i++){
int a=read(),b=read(),c=read();
ins(a,b,c);
}
spfa();
printf("%d",dis
);
return 0;
}