POJ 1523 SPF Problem Solving report

Idea: Use the Tarjan algorithm to find the cut point, in the enumeration to remove each cut point can form the number of Unicom block.

Note: Later I looked at the other code, found that my enumeration of the way to cut points is a rather stupid way, we can completely in the Tarjan process to find out the answer, introduce the discussion:

If this cut point is the root node, in the Tarjan algorithm to find a few children node (Low[v] >= dfn[u]), he can cut a few unicom block, if the cut is a child node, then he formed the number of Unicom block +1, because he also has a father node indirectly or directly connected to the side.

The code is as follows:

#include <map>#include<cstdio>#include<cstring>#include<queue>#include<algorithm>using namespacestd;#defineMAXN 1010structedge{intTO,NXT;} EDGE[MAXN*Ten];intHEAD[MAXN],LOW[MAXN],DFN[MAXN],MARK[MAXN],VIS[MAXN];intTot,all,son,start,tail;voidAdd_edge (intUintv) {edge[tot].to=v; EDGE[TOT].NXT=Head[u]; Head[u]= tot++;}voidinit () {memset (Low,0,sizeof(low)); memset (DFN,0,sizeof(DFN)); memset (Mark,0,sizeof(Mark)); All=0; Son=0;}voidTarjan (intUintFA) {Dfn[u]= Low[u] = + +All ;  for(inti = Head[u]; I! =-1; i =edge[i].nxt) {        intv =edge[i].to; if(!Dfn[v])            {Tarjan (v,u); Low[u]=min (low[v],low[u]); if(Low[v] >=Dfn[u]) {                if(U = = start) son++; ElseMark[u] =1; }        }        Else if(v! = FA) Low[u] =min (low[u],dfn[v]); }    return ;}voidBFsintXintcant) {Queue<int>que;  while(!que.empty ()) Que.pop ();    Que.push (x); VIS[X]=1;  while(!Que.empty ()) {        intnum =Que.front ();        Que.pop ();  for(inti = Head[num]; I! =-1; i =edge[i].nxt) {            intv =edge[i].to; if(v! = Cant &&!Vis[v])                {Que.push (v); VIS[V]=1; }        }    }    return ;}intMain () {intb; intCA =0;  while(~SCANF ("%d",&a)) {if(!a) Break; Start=0, tail =0; scanf ("%d",&b); Start=min (A, b); Tail=Max (A, b); Tot=0; memset (Head,-1,sizeof(head));        Add_edge (A, b);        Add_edge (B,a);  while(~SCANF ("%d",&a)) {if(!a) Break; scanf ("%d",&b);            Add_edge (A, b);            Add_edge (B,a); Start=min (A, B), start); Tail=Max (A, b), tail;        } init (); Tarjan (Start,-1); if(Son >=2) Mark[start] =1; intsubnets =0, SPF =0; printf ("Network #%d\n",++CA); BOOLFlag =true;  for(inti = start; I <= tail; i++)        {            if(Mark[i]) {flag=false; printf ("SPF node%d leaves", i); memset (Vis,0,sizeof(VIS)); Subnets=0;  for(intj = Start;j <= tail;j++)                {                    if(j = = i)Continue; if(!Vis[j]) {Subnets++;                    BFS (J,i); }} printf ("%d subnets\n", subnets); }        }        if(flag) puts ("No SPF Nodes"); Puts (""); }    return 0;}

POJ 1523 SPF Problem Solving report