hdu-3594 Cactus (Strong connectivity)

http://acm.hdu.edu.cn/showproblem.php?pid=3594

Determines whether a given graph is strongly connected, and each edge belongs to only one connected component.

A strong connection is determined by determining whether the vertex number is 1 after the indent.

Then, in the process of shrinking, if a ring has been produced, and the parent node of the present node has a parent node, there must be more than one ring.

Finally, we must judge each node to belong to only one unicom component, otherwise it does not meet the requirements.

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 50100 + //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 } - //Dnf[i] Indicates that the DFS is the first time to traverse to point I Wu //Low[u] indicates that a subtree with a U point as the parent node can connect to the DFN value of the topmost point in the stack (in other words, the smallest dfn, because the DFN at the top is the smallest) - 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) About intTaj//connecting branch designator, starting from 1 $ intBelong[n];//Belong[i] represents the connected branch where I point belongs - BOOLInstack[n],flag; -vector<int> Bcc[n];//marking starting from 1 -  A voidTarjan (intU,intFA) { +Dfn[u] = Low[u] = + +Time ; theStack[top + +] =u; -Instack[u] =1 ; $  the      for(inti = Head[u]; ~i; i =Edge[i].nex) { the         intv =edge[i].to; the         if(Dfn[v] = =-1) the         { - Tarjan (V, u); inLow[u] =min (Low[u], low[v]); the             if(Dfn[u] <Low[v]) the             { AboutEdge[i].sign =1;//to cut the bridge . the             } the         } the         Else if(Instack[v]) +         { -Low[u] =min (Low[u], dfn[v]); the             if(Dfn[v]!=low[v]) flag=1;//parent node is not yet a root nodeBayi         } the     } the     if(Low[u] = =Dfn[u]) { -         intNow ; -Taj + +; Bcc[taj].clear (); the          Do{ thenow = stack[--top]; theInstack[now] =0 ; the             if(belong[now]!=-1) flag=1;//Each node must belong to only one Unicom component -Belong [Now] =Taj; the Bcc[taj].push_back (now); the} while(Now! =u); the     }94 } the  the voidTarjan_init (intAll ) { thememset (DFN,-1,sizeof(DFN));98memset (Instack,0,sizeof(Instack)); Aboutmemset (belong,-1,sizeof(Belong)); -top = time = Taj =0;101      for(intI=1; i<=all;i++)if(dfn[i]==-1) Tarjan (i, I);//Notice the start point!!! 102 }103vector<int>G[n];104 intDu[n]; the voidSuodian () {106Memset (Du,0,sizeof(du));107      for(inti =1; I <= Taj; i++) g[i].clear ();108      for(inti =0; i < Edgenum; i++){109         intU = belong[edge[i]. from], V =belong[edge[i].to]; the         if(u!=v)111         { theG[u].push_back (v), du[v]++;113            //printf ("%d%d\n", u,v); the         } the     } the }117 voidInit () {memset (head,-1,sizeof(head)); edgenum=0;}118 intMain ()119 { -     //Read ();121     intt,a,b;122scanf"%d",&t);123      while(t--)124     { thescanf"%d",&n);126 init ();127flag=0; -          while(1)129         { thescanf"%d%d",&a,&b);131             if(a==0&&b==0) Break; theAdd (A +1, B +1);133         }134 tarjan_init (n);135 Suodian ();136 137         if(taj==1&&flag==0) puts ("YES");138         ElsePuts"NO");139     } $     return 0;141}

hdu-3594 Cactus (Strong connectivity)