Solving the problem of edge-to-double connectivity (structural edge dual connected graph) POJ3352 (Road construction)

Topic Link: Portal

The main topic: give you a pair of non-direction, ask at least how many edges to make the diagram become a double unicom

Topic Idea: Tarjan algorithm to shrink point, after the reduction of the number of leaf nodes of 1 degrees, need to add the number of edges (leaf+1)/2

1#include <iostream>2#include <cstdio>3#include <cstdlib>4#include <cmath>5#include <algorithm>6#include <cstring>7#include <stack>8#include <cctype>9#include <queue>Ten#include <string> One#include <vector> A#include <Set> -#include <map> -#include <climits> the #defineLson Root<<1,l,mid - #defineRson Root<<1|1,mid+1,r - #defineFi first - #defineSe Second + #definePing (x, y) ((x-y) * (x-y)) - #defineMST (x, y) memset (x,y,sizeof (x)) + #defineMCP (x, y) memcpy (x,y,sizeof (y)) A #defineMin (x, y) (x<y?x:y) at #defineMax (x, y) (x>y?x:y) - using namespacestd; - #defineGamma 0.5772156649015328606065120 - #defineMOD 1000000007 - #defineINF 0x3f3f3f3f - #defineN 5005 in #defineMAXN 10005 -typedefLong LongLL; totypedef pair<int,int>PII; +  -vector<int>v[1005]; the intN,m,hcnt,deep; * structnode{ $     intTo,next;Panax Notoginseng Node () {} -Node (intAintb): to (a), next (b) {} the }node[n]; + intHead[n],vis[n],low[n],dfn[n]; A intD[n]; the  +InlinevoidAddintXinty) { -node[hcnt]=Node (y,head[x]); $head[x]=hcnt++; $ } -  -Inlinevoidinit () { theMST (D,0); -MST (VIS,0); vis[1]=1;WuyiMST (head,-1); theHcnt=0; -deep=1; Wulow[1]=dfn[1]=1; - } About  $ voidDfsintXintfather) { -      for(intI=head[x];~i;i=Node[i].next) { -         intE=node[i].to; -         if(E==father)Continue; A         if(Vis[e]) low[x]=min (low[x],dfn[e]); +         Else{ thevis[e]=1; -low[e]=dfn[e]=++Deep ; $ DFS (e,x); thelow[x]=min (low[x],low[e]); the         } the     } the } -  in intMain () { the     intI,j,group,case=0, x, y; the      while(SCANF ("%d%d", &n,&m)! =EOF) { About          for(i=0; i<=n;++i) V[i].clear (); the init (); the          while(m--){ thescanf"%d%d",&x,&y); + Add (x, y); - Add (y,x); theV[x].push_back (y);///Two-point UnicomBayiV[y].push_back (x);///used to calculate degrees after a pinch point the         } theDfs1,-1);///Tarjan Algorithm -         intleaf=0; -          for(i=1; i<=n;++i) the         if(V[i].size ()) the          for(j=0; J<v[i].size (); + +j) { the             intE=V[i][j]; the             if(low[i]!=Low[e]) -d[low[i]]++; the         } the          for(i=0; i<=deep;++i) the             if(d[i]==1)++Leaf;94printf"%d\n", (leaf+1)/2); the     } the     return 0; the}

Solving the problem of edge-to-double connectivity (structural edge dual connected graph) POJ3352 (Road construction)