hdu-3836 equivalent sets (strong connectivity)

http://acm.hdu.edu.cn/showproblem.php?pid=3836

The judgment requires at least a few edges to make the graph strong and connected.

The point after which the graph is indented and the points with a degree of 0 are counted, and the maximum value in both is the edge that needs to be connected,

For example, assuming that there are more than 0 points, each time a point with a degree of 0 is connected to a point with an edge of 0, a ring is formed.

So a strong connected component is formed, and the same can be obtained with a degree of more than 0 points.

This code with g++ Re, C + + in order to AC.

1#include <iostream>2#include <cstdio>3#include <cmath>4#include <vector>5#include <cstring>6#include <algorithm>7#include <string>8#include <Set>9#include <functional>Ten#include <numeric> One#include <sstream> A#include <stack> -#include <map> -#include <queue> the  - #defineCL (arr, Val) memset (arr, Val, sizeof (arr)) -  - #definell Long Long + #defineINF 0x7f7f7f7f - #defineLC L,m,rt<<1 + #defineRC M + 1,r,rt<<1|1 A #definePi ACOs (-1.0) at  - #defineL (x) (x) << 1 - #defineR (x) (x) << 1 | 1 - #defineMID (L, R) (L + R) >> 1 - #defineMin (x, y) (x) < (y)? (x): (y) - #defineMax (x, y) (x) < (y)? (y): (x) in #defineE (x) (1 << (x)) - #defineIabs (x) (x) < 0? -(x): (x) to #defineOut (x) printf ("%i64d\n", X) + #defineLowbit (x) (x) & (-X) - #defineRead () freopen ("A.txt", "R", stdin) the #defineWrite () freopen ("Dout.txt", "w", stdout); *  $ using namespacestd;Panax Notoginseng #defineN 20100 - //n is the maximum number of points the #defineM 150100 + //m is the maximum number of sides A intN, M;//N M is the number of points and sides the  + structedge{ -     int  from, to, NEX; $     BOOLSign//whether it is a bridge $}edge[m<<1]; - intHead[n], edgenum; - voidAddintUintV) {//the beginning and end of the edge theEdge E={u, V, Head[u],false}; -Edge[edgenum] =E;WuyiHead[u] = edgenum++; the } -  Wu intDfn[n], Low[n], Stack[n], top, time;//Low[u] is the dfn[v of the point set {U-point and subtree in the root of the U-point (all reverse arcs) that can point to (the nearest ancestor V from the root ) (i.e., V-point timestamp) - intTaj//connecting branch designator, starting from 1 About intBelong[n];//Belong[i] represents the connected branch where I point belongs $ BOOLInstack[n]; -vector<int> Bcc[n];//marking starting from 1 -  - voidTarjan (intU,intFA) { ADfn[u] = Low[u] = + +Time ; +Stack[top + +] =u; theInstack[u] =1 ; -  $      for(inti = Head[u]; ~i; i =Edge[i].nex) { the         intv =edge[i].to; the         if(Dfn[v] = =-1) the         { the Tarjan (V, u); -Low[u] =min (Low[u], low[v]); in             if(Dfn[u] <Low[v]) the             { theEdge[i].sign =1;//to cut the bridge . About             } the         } the         Else if(Instack[v]) Low[u] =min (Low[u], dfn[v]); the     } +     if(Low[u] = =Dfn[u]) { -         intNow ; theTaj + +; Bcc[taj].clear ();Bayi          Do{ thenow = stack[--top]; theInstack[now] =0 ; -Belong [Now] =Taj; - Bcc[taj].push_back (now); the} while(Now! =u); the     } the } the  - voidTarjan_init (intAll ) { thememset (DFN,-1,sizeof(DFN)); thememset (Instack,0,sizeof(Instack)); thetop = time = Taj =0;94      for(intI=1; i<=all;i++)if(dfn[i]==-1) Tarjan (i, I);//Notice the start point!!!  the } thevector<int>G[n]; the intDu[n];98 voidSuodian () { AboutMemset (Du,0,sizeof(du)); -      for(inti =1; I <= Taj; i++) g[i].clear ();101      for(inti =0; i < Edgenum; i++){102         intU = belong[edge[i]. from], V =belong[edge[i].to];103         if(u!=v)104         { theG[u].push_back (v), du[v]++;106            //printf ("%d%d\n", u,v);107         }108     }109 } the voidInit () {memset (head,-1,sizeof(head)); edgenum=0;}111 intMain () the {113     //Read (); the     intb; the      while(~SCANF ("%d%d",&n,&m)) the     {117 init ();118         //scanf ("%d%d", &n,&m);119          for(intI=0; i<m;i++) -         {121scanf"%d%d",&a,&b);122 Add (A, b);123         }124 tarjan_init (n); the Suodian ();126         if(taj==1) {printf ("0\n");Continue;}//The diagram is strong connectivity .127         intx1=0, x2=0; -          for(intI=1; i<=taj;i++)129         { the             if(g[i].size () = =0) x1++;//number of points with a degree of 0131             if(du[i]==0) x2++;//the number of degrees is 0 points the         }133         //printf ("%d%d\n", x1,x2);134printf"%d\n", Max (x1,x2));135     }136     return 0;137}

hdu-3836 equivalent sets (strong connectivity)