USCAO3.26Sweet Butter（SPFA)

最短路复杂度估计错误 以为SPFA是N*m的 用了dij超时 用SPFA直接跑就好了

O（k*e) K 一般为2,3；

  1 /*

  2     ID: shangca2

  3     LANG: C++

  4     TASK: butter

  5  */

  6 #include <iostream>

  7 #include<cstdio>

  8 #include<cstring>

  9 #include<algorithm>

 10 #include<stdlib.h>

 11 #include<queue>

 12 using namespace std;

 13 #define M 1500

 14 #define P 850

 15 #define N 550

 16 #define INF 0xfffffff

 17 struct node

 18 {

 19     int u,v,w,next;

 20 }ed[M<<1];

 21 int t,head[P],dis[P],a[N],n,p,c,vis[P],f[P],k[P],o[P][P];

 22 void init()

 23 {

 24     t = 0;

 25     memset(head,-1,sizeof(head));

 26 }

 27 void add(int u,int v,int w)

 28 {

 29     ed[t].u = u;

 30     ed[t].v = v;

 31     ed[t].w = w;

 32     ed[t].next = head[u];

 33     head[u] = t++;

 34 }

 35 void spfa(int st)

 36 {

 37     int i;

 38     memset(vis,0,sizeof(vis));

 39     for(i = 1; i <= p ; i++)

 40     dis[i] = INF;

 41     dis[st] = 0;

 42     queue<int>q;

 43     vis[st] = 1;

 44     q.push(st);

 45     while(!q.empty())

 46     {

 47         int u = q.front();

 48         q.pop();

 49         vis[u] = 0;

 50         for(i = head[u]; i != -1 ;i = ed[i].next)

 51         {

 52             int v = ed[i].v;

 53             if(ed[i].w+dis[u]<dis[v])

 54             {

 55                 dis[v] = ed[i].w+dis[u];

 56                 if(!vis[v])

 57                 {

 58                     vis[v] = 1;

 59                     q.push(v);

 60                 }

 61             }

 62         }

 63     }

 64     for(i = 1; i <= p ; i++)

 65     {

 66         if(o[st][i]>dis[i])

 67         {

 68             o[st][i] = dis[i];

 69             o[i][st] = dis[i];

 70         }

 71     }

 72 }

 73 int main()

 74 {

 75     freopen("butter.in","r",stdin);

 76     freopen("butter.out","w",stdout);

 77     int i,j,u,v,w;

 78     init();

 79     cin>>n>>p>>c;

 80     for(i  =0  ;i <= p ; i++)

 81         for(j = 1; j <= p ; j++)

 82         o[i][j] = INF;

 83     for(i = 1; i <= n ;i++)

 84         cin>>a[i];

 85     for(i = 1; i <= c ;i++)

 86     {

 87         scanf("%d%d%d",&u,&v,&w);

 88         add(u,v,w);

 89         add(v,u,w);

 90     }

 91     for(i = 1; i <= n ;i++)

 92     {

 93         if(!f[a[i]])

 94         {

 95             f[a[i]] = 1;

 96             spfa(a[i]);

 97         }

 98     }

 99     int minz = INF;

100     for(i = 1; i <= p ; i++)

101     {

102         int s = 0;

103         for(j = 1 ; j <= n ; j++)

104         {

105             if(a[j]!=i)

106             s+=o[a[j]][i];

107         }

108         minz = min(minz,s);

109     }

110     printf("%d\n",minz);

111     return 0;

112 }

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