hdu 3191 How Many Paths Are There

http://acm.hdu.edu.cn/showproblem.php?pid=3191

这道题求次短路经和路径数

  1 #include <cstdio>

  2 #include <cstring>

  3 #include <vector>

  4 #include <queue>

  5 #include <algorithm>

  6 #define maxn 2000

  7 using namespace std;

  8 const int inf=1<<30;

  9 struct edge

 10 {

 11     int v,w;

 12 };

 13 

 14 struct node

 15 {

 16     int d,v;

 17     int mark;

 18     bool operator < (const node &a)const

 19     {

 20         if(d!=a.d)

 21             return d>a.d;

 22         return v>a.v;

 23     }

 24 };

 25 

 26 vector<edge>edges[maxn];

 27 int dis[maxn][3];

 28 int vis[maxn][3];

 29 int path[maxn][3];

 30 int n,m,a,b,c,s1,f;

 31 node st;

 32 

 33 

 34 void inti()

 35 {

 36     for(int i=0; i<=n; i++)

 37     {

 38         dis[i][1]=dis[i][2]=inf;

 39     }

 40     memset(path,0,sizeof(path));

 41     memset(vis,false,sizeof(vis));

 42 }

 43 

 44 void dijkstra(int s,int e)

 45 {

 46     inti();

 47     priority_queue<node>q;

 48     dis[s][1]=0;

 49     path[s][1]=1;

 50     memset(vis,false,sizeof(vis));

 51     st.d=0;

 52     st.v=s;

 53     st.mark=1;

 54     q.push(st);

 55     while(!q.empty())

 56     {

 57         node st1=q.top();

 58         q.pop();

 59         if(vis[st1.v][st1.mark]) continue;

 60         vis[st1.v][st1.mark]=true;

 61         for(int i=0; i<(int)edges[st1.v].size(); i++)

 62         {

 63             int v1=edges[st1.v][i].v;

 64             int w1=edges[st1.v][i].w;

 65             if(!vis[v1][1]&&st1.d+w1<dis[v1][1])

 66             {

 67                 if(dis[v1][1]!=inf)

 68                 {

 69                     dis[v1][2]=dis[v1][1];

 70                     path[v1][2]=path[v1][1];

 71                     st.d=dis[v1][2];

 72                     st.v=v1;

 73                     st.mark=2;

 74                     q.push(st);

 75                 }

 76                 dis[v1][1]=st1.d+w1;

 77                 path[v1][1]=path[st1.v][st1.mark];

 78                 st.v=v1;

 79                 st.mark=1;

 80                 st.d=dis[v1][1];

 81                 q.push(st);

 82             }

 83             else if(!vis[v1][1]&&st1.d+w1==dis[v1][1])

 84             {

 85                 path[v1][1]+=path[st1.v][st1.mark];

 86             }

 87             else if(!vis[v1][2]&&st1.d+w1<dis[v1][2])

 88             {

 89                 dis[v1][2]=st1.d+w1;

 90                 path[v1][2]=path[st1.v][st1.mark];

 91                 st.d=dis[v1][2];

 92                 st.v=v1;

 93                 st.mark=2;

 94                 q.push(st);

 95             }

 96             else if(!vis[v1][2]&&st1.d+w1==dis[v1][2])

 97             {

 98                 path[v1][2]+=path[st1.v][st1.mark];

 99             }

100         }

101     }

102 }

103 

104 int main()

105 {

106     while(scanf("%d%d%d%d",&n,&m,&s1,&f)!=EOF)

107     {

108         inti();

109         for(int i=0; i<=n; i++) edges[i].clear();

110         for(int i=0; i<m; i++)

111         {

112             scanf("%d%d%d",&a,&b,&c);

113             edge m1;

114             m1.v=b;

115             m1.w=c;

116             edges[a].push_back(m1);

117         }

118         dijkstra(s1,f);

119         printf("%d %d\n",dis[f][2],path[f][2]);

120     }

121     return 0;

122 }

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