POJ1511 Invitation Cards（多源单汇最短路）

 1 #include<cstdio>
 2 #include<cstring>
 3 #include<queue>
 4 #include<algorithm>
 5 using namespace std;
 6 #define MAXN 1111111
 7 #define MAXM 1111111
 8 
 9 inline void in(int &ret){
10     char c; ret=0;
11     while(c=getchar(),c<‘0‘||c>‘9‘);
12     while(c>=‘0‘&&c<=‘9‘) ret=ret*10+c-‘0‘,c=getchar();
13 }
14 void out(long long x){
15     if(x>9) out(x/10);
16     putchar(x%10+‘0‘);
17 }
18 
19 struct Edge{
20     int v,cost,next;
21 }edge[MAXM<<1];
22 int head[MAXN],rhead[MAXN],NE;
23 void addEdge(int a,int b,int c){
24     edge[NE].v=b; edge[NE].cost=c; edge[NE].next=head[a];
25     head[a]=NE++;
26     edge[NE].v=a; edge[NE].cost=c; edge[NE].next=rhead[b];
27     rhead[b]=NE++;
28 }
29 
30 int n,m;
31 int d[MAXN];
32 bool vis[MAXN];
33 void SPFA(){
34     memset(d,127,sizeof(d));
35     d[1]=0;
36     memset(vis,0,sizeof(vis));
37     vis[1]=1;
38     queue<int> que;
39     que.push(1);
40     while(!que.empty()){
41         int u=que.front(); que.pop();
42         for(int i=head[u];i !=-1; i=edge[i].next){
43             int v=edge[i].v;
44             if(d[v]>d[u]+edge[i].cost){
45                 d[v]=d[u]+edge[i].cost;
46                 if(!vis[v]){
47                     vis[v]=1;
48                     que.push(v);
49                 }
50             }
51         }
52         vis[u]=0;
53     }
54 }
55 void rSPFA(){
56     memset(d,127,sizeof(d));
57     d[1]=0;
58     memset(vis,0,sizeof(vis));
59     vis[1]=1;
60     queue<int> que;
61     que.push(1);
62     while(!que.empty()){
63         int u=que.front(); que.pop();
64         for(int i=rhead[u]; i!=-1; i=edge[i].next){
65             int v=edge[i].v;
66             if(d[v]>d[u]+edge[i].cost){
67                 d[v]=d[u]+edge[i].cost;
68                 if(!vis[v]){
69                     vis[v]=1;
70                     que.push(v);
71                 }
72             }
73         }
74         vis[u]=0;
75     }
76 }
77 
78 int main(){
79     int t,a,b,c;
80     in(t);
81     while(t--){
82         NE=0;
83         memset(head,-1,sizeof(head));
84         memset(rhead,-1,sizeof(rhead));
85         in(n); in(m);
86         while(m--){
87             in(a); in(b); in(c);
88             addEdge(a,b,c);
89         }
90         long long res=0;
91         SPFA();
92         for(int i=1; i<=n; ++i) res+=d[i];
93         rSPFA();
94         for(int i=1; i<=n; ++i) res+=d[i];
95         out(res); putchar(‘\n‘);
96     }
97     return 0;
98 }