HDU 3191 How Many Paths Are There

 1 #include <iostream>
 2 #include <cstdio>
 3 #include <cstring>
 4 #include <cmath>
 5 #include <algorithm>
 6 #include <climits>
 7 #include <vector>
 8 #include <queue>
 9 #include <cstdlib>
10 #include <string>
11 #include <set>
12 #include <stack>
13 #define LL long long
14 #define pii pair<int,int>
15 #define INF 0x3f3f3f3f
16 using namespace std;
17 const int maxn = 55;
18 struct arc {
19     int to,w,next;
20     arc(int x = 0,int y = 0,int z = -1) {
21         to = x;
22         w = y;
23         next = z;
24     }
25 };
26 arc e[10000];
27 int head[maxn],d[maxn][2],cnt[maxn][2],tot,big,ed,n,m;
28 bool vis[maxn][2];
29 void add(int u,int v,int w){
30     e[tot] = arc(v,w,head[u]);
31     head[u] = tot++;
32 }
33 void dijkstra(){
34     for(int i = 0; i <= n; i++){
35         vis[i][0] = vis[i][1] = false;
36         cnt[i][0] = cnt[i][1] = 0;
37         d[i][0] = d[i][1] = INF;
38     }
39     d[big][0] = 0;
40     cnt[big][0] = 1;
41     while(true){
42         int u,Min = INF,flag;
43         for(int i = 0; i < n; i++){
44             if(!vis[i][0] && d[i][0] < Min)
45                 Min = d[u = i][flag = 0];
46             else if(!vis[i][1] && d[i][1] < Min)
47                 Min = d[u = i][flag = 1];
48         }
49         if(u == ed && flag || Min == INF) break;
50         vis[u][flag] = true;
51         for(int i = head[u]; ~i; i = e[i].next){
52             int v = e[i].to;
53             int w = d[u][flag] + e[i].w;
54             if(d[v][0] > w){
55                 if(d[v][0] < INF){
56                     d[v][1] = d[v][0];
57                     cnt[v][1] = cnt[v][0];
58                 }
59                 d[v][0] = w;
60                 cnt[v][0] = cnt[u][flag];
61             }else if(d[v][0] == w)
62                 cnt[v][0] += cnt[u][flag];
63             else if(d[v][1] > w){
64                 d[v][1] = w;
65                 cnt[v][1] = cnt[u][flag];
66             }else if(d[v][1] == w) cnt[v][1] += cnt[u][flag];
67         }
68     }
69     printf("%d %d\n",d[ed][1],cnt[ed][1]);
70 }
71 int main(){
72     int u,v,w;
73     while(~scanf("%d %d %d %d",&n,&m,&big,&ed)){
74         memset(head,-1,sizeof(head));
75         for(int i = tot = 0; i < m; i++){
76             scanf("%d %d %d",&u,&v,&w);
77             add(u,v,w);
78         }
79         dijkstra();
80     }
81     return 0;
82 }