HDU 1863 unblocked Project (minimum spanning tree, prim)

Test instructions: Given the edges and points of the graph, the cost of minimum spanning tree is required, note: Some points are unreachable, that is, there may be multiple connected graphs. For example, 4 points, 2 sides: 1-2, 3-4.

Idea: If you can't connect all the dots, then output '? '. Previously thought that each point as long as there is an edge attached to be able to generate a tree, in fact, it can be each point although there is a side can reach, but given is actually two diagram, such as the above example. Others follow regular prim.

1#include <bits/stdc++.h>2 using namespacestd;3 Const intn= the;4 Const intMod=0x7f7f7f7f;5 intV[n][n];//Rights6 intVis[n];7 intLow[n];//to the minimum right of each point8 9 Ten intPrimintN) One { A     intpos=vis[1]=1;//starting from point 1 -      for(intI=2; i<=n; i++) low[i]=v[1][i];//at present to each point of the smallest right -     intans=0; the      for(intI=1; i<n; i++)//Take the other n-1. -     { -         intbig=MoD; -          for(intj=2; j<=n; J + +)//The least right side of the search +         { -             if(!vis[j] && low[j]<big)//not browsed, at present can reach, the right small +             { Apos=J; atbig=Low[j]; -             } -         } -         if(Big==mod)return 0;//cannot be reached.  -ans+=Big; -vis[pos]++;//have viewed in          for(intj=2; j<=n; J + +)//update weights to each point -             if(!vis[j] && v[pos][j]<mod && low[j]>v[pos][j]) low[j]=v[pos][j];//not browsed, there is a way up, shorter to     } +     returnans; - } the  *  $ Panax Notoginseng  - intMain () the { +Freopen ("Input.txt","R", stdin); A     intN, M, a, B, t; the      while(SCANF ("%d%d", &n, &m), N) +     { -  $memset (CNT,0,sizeof(CNT)); $memset (Vis,0,sizeof(Vis)); -memset (V,0x7f,sizeof(v));//set to not reach -  the          for(intI=0; i<n; i++) -         {Wuyiscanf"%d%d%d",&a,&b,&t); thev[a][b]=v[b][a]=T; -         } Wu         intans=Prim (m); -         if(ANS) printf ("%d\n", ans); About         Elseprintf"? \ n"); $     } -     return 0; -}

AC Code

HDU 1863 unblocked Project (minimum spanning tree, prim)