"Kruskal+ greedy thought" bzoj3624-[apio2008] Free Road

Long live the National Day!!!!!

"The main topic"

Given an untyped graph, there are two types of edges that are 0 and 1. Find a minimum spanning tree so that side 0 has k bars.

Ideas

Run two times Kruskal.

The first time to select the Edge 1, and then determine which side 0 is not connected, then these side 0 must be selected. If you have to select an edge 0 greater than K, then the direct output is no solution.

The second time first merge then must select the Edge 0, and then in the remaining side 0 left or right there is no connected to the selection. If you select all of the back 0 of the number is still not to K, then the direct output of no solution.

Cut down to the common Kruskal method to merge the side 1.

1#include <iostream>2#include <cstdio>3#include <algorithm>4#include <cstring>5#include <vector>6 using namespacestd;7 Const intmaxn=20000+ -;8 Const intmaxm=100000+ -;9 structEdgeTen { One     intu,v; A }EDGE[MAXM]; - intn,m,k; - intVIS[MAXM]; the intL,r; - intFA[MAXN],H[MAXN]; -vector<int>Mustchoose; -  + voidInitset () { for(intI=1; i<=n;i++) fa[i]=i,h[i]=1;} -  + intFindintx) A { at     intR=x; -      while(fa[r]!=r) r=Fa[r]; -      while(fa[x]!=R) -     { -         inttmp=Fa[x]; -fa[x]=R; inx=Fa[x]; -     } to     returnR; + } -  the voidUnionset (intAintb) * { $     if(h[a]>=H[b])Panax Notoginseng     { -fa[b]=A; the         if(H[a]==h[b]) h[a]++; +     } A     Elsefa[a]=b; the } +  - voidInit () $ { $scanf"%d%d%d",&n,&m,&k); -L=0, r=m+1; -      for(intI=1; i<=m;i++)  the     { -         intu,v,c;Wuyiscanf"%d%d%d",&u,&v,&c); the         if(c) edge[++l]=(Edge) {u,v}; -             Elseedge[--r]=(Edge) {u,v}; Wu     } - } About  $ voidSolve () - { -     intt=0;  - Initset (); A      for(intI=1; i<=m;i++) +     { the         intFa=find (edge[i].u), fb=find (EDGE[I].V); -         if(fa!=FB) $         { the Unionset (FA,FB); the             if(i>=R) the             { thevis[i]=1; -t++; in Mustchoose.push_back (i); the             } the         } About     } the     if(t>k) the     { thePuts"No solution"); +         return; -     } the     //Find the Cobblestone road you have to chooseBayi      the Initset (); the      for(intI=0; I<mustchoose.size (); i++) -     { -         intFa=find (edge[mustchoose[i]].u), fb=find (EDGE[MUSTCHOOSE[I]].V); the Unionset (FA,FB);  the     } the      for(inti=r;i<=m;i++) the         if(T<k &&!)Vis[i]) -         { the             intFa=find (edge[i].u), fb=find (EDGE[I].V); the             if(fa!=FB) the             {94 Unionset (FA,FB); thevis[i]=1; thet++; the             }98         } About     if(t<k) -     {101Puts"No solution");102         return;103     }104     //first select the cobblestone path you want, and then fill it with other cobblestone paths the     106      for(intI=1; i<=l;i++)107     {108         intFa=find (edge[i].u), fb=find (EDGE[I].V);109         if(fa!=FB) the         {111 Unionset (FA,FB); thevis[i]=1;113         } the     }  the      for(intI=1; i<=l;i++)if(Vis[i]) printf ("%d%d%d\n", EDGE[I].U,EDGE[I].V,1); the      for(inti=r;i<=m;i++)if(Vis[i]) printf ("%d%d%d\n", EDGE[I].U,EDGE[I].V,0);117 }118 119 intMain () - {121 init ();122 solve ();123}

"Kruskal+ greedy thought" bzoj3624-[apio2008] Free Road