[题解]UVA10986 Sending email

链接：http://vjudge.net/problem/viewProblem.action?id=24941

描述：n个点，m条边的无向图，寻找从S到T的最短路。

思路：基础的单源点最短路 用Dijkstra或spfa都可以解决

这是我的实现：

  1 #include <iostream>
  2 #include <cstdio>
  3 #include <cstring>
  4 #include <queue>
  5 using namespace std;
  6 #define MaxN 20020
  7 #define MaxM 100020
  8 struct node
  9 {
 10     int v,dist;
 11     node *next;
 12 };
 13 node Edge[MaxM];
 14 node *cnt=&Edge[0];
 15 node *adj[MaxN];
 16 int dist[MaxN];
 17 int N,INF;
 18 int n,m,S,T;
 19 inline void Get_int(int &Ret)
 20 {
 21     char ch;
 22     bool flag=false;
 23     for(;ch=getchar(),ch<'0'||ch>'9';)
 24         if(ch=='-')
 25             flag=true;
 26     for(Ret=ch-'0';ch=getchar(),ch>='0'&&ch<='9';Ret=Ret*10+ch-'0');
 27     flag&&(Ret=-Ret);
 28 }
 29 inline void Clean()
 30 {
 31     memset(Edge,0,sizeof(Edge));
 32     cnt=&Edge[0];
 33     memset(adj,0,sizeof(adj));
 34 }
 35 inline void Addedge(int u,int v,int w)
 36 {
 37     node *p=++cnt;
 38     p->v=v;
 39     p->dist=w;
 40     p->next=adj[u];
 41     adj[u]=p;
 42
 43     p=++cnt;
 44     p->v=u;
 45     p->dist=w;
 46     p->next=adj[v];
 47     adj[v]=p;
 48 }
 49 inline void Read_Build()
 50 {
 51     Get_int(n);Get_int(m);Get_int(S);Get_int(T);
 52     int i,u,v,w;
 53     for(i=1;i<=m;++i)
 54     {
 55         Get_int(u);Get_int(v);Get_int(w);
 56         Addedge(u,v,w);
 57     }
 58 }
 59 struct cmp
 60 {
 61     bool operator()(node a,node b)
 62     {
 63         return a.dist>b.dist;
 64     }
 65 };
 66 priority_queue <node, vector<node>, cmp> q;
 67 void Dijkstra(int s)
 68 {
 69     node c,d;
 70     node *p;
 71     int i,j,k;
 72     memset(dist,0x3f,sizeof(dist));
 73     INF=dist[s];
 74     dist[s]=0;
 75     c.v=s;c.dist=0;
 76     q.push(c);
 77     while(!q.empty())
 78     {
 79         d=q.top();q.pop();
 80         j=d.v;
 81         for(p=adj[j];p!=NULL;p=p->next)
 82         {
 83             k=p->v;
 84             if(dist[k]>dist[j]+p->dist)
 85             {
 86                 dist[k]=dist[j]+p->dist;
 87                 d.v=k;d.dist=dist[k];
 88                 q.push(d);
 89             }
 90         }
 91     }
 92 }
 93 inline void Print()
 94 {
 95     if(dist[T]==INF)
 96         printf("unreachable\n");
 97     else
 98         printf("%d\n",dist[T]);
 99 }
100 int main()
101 {
102     Get_int(N);
103     for(int i=1;i<=N;i++)
104     {
105         printf("Case #%d: ",i);
106         Clean();
107         Read_Build();
108         Dijkstra(S);
109         Print();
110     }
111     return 0;
112 }