bzoj2015[Usaco2010 Feb]Chocolate Giving*

 1 #include <cstdio>
 2 #include <cstring>
 3 #include <algorithm>
 4 #include <queue>
 5 #define ll long long
 6 #define inc(i,j,k) for(int i=j;i<=k;i++)
 7 #define maxn 50010
 8 #define INF 0x3fffffff
 9 using namespace std;
10 
11 inline ll read(){
12     char ch=getchar(); ll f=1,x=0;
13     while(ch<‘0‘||ch>‘9‘){if(ch==‘-‘)f=-1; ch=getchar();}
14     while(ch>=‘0‘&&ch<=‘9‘)x=x*10+ch-‘0‘,ch=getchar();
15     return f*x;
16 }
17 
18 struct e{int t,w,n;}; e es[maxn*4]; int g[maxn],ess;
19 void pe(int f,int t,int w){es[++ess]=(e){t,w,g[f]}; g[f]=ess; es[++ess]=(e){f,w,g[t]}; g[t]=ess;}
20 int n,m,b,d[maxn]; bool inq[maxn]; queue<int>q;
21 void spfa(){
22     while(!q.empty())q.pop(); memset(inq,0,sizeof(inq)); inc(i,1,n)d[i]=INF;
23     q.push(1); inq[1]=1; d[1]=0;
24     while(!q.empty()){
25         int x=q.front(); q.pop(); inq[x]=0;
26         for(int i=g[x];i;i=es[i].n)if(d[es[i].t]>d[x]+es[i].w){
27             d[es[i].t]=d[x]+es[i].w; if(!inq[es[i].t])q.push(es[i].t),inq[es[i].t]=1;
28         }
29     }
30 }
31 int main(){
32     n=read(); m=read(); b=read();
33     inc(i,1,m){int a=read(),b=read(),c=read(); pe(a,b,c);} spfa();
34     inc(i,1,b){int a=read(),b=read(); printf("%d\n",d[a]+d[b]);} return 0;
35 }