POJ-1523 SPF (Tarjan for cutting points)

Title Link:http://poj.org/problem?id=1523

The main topic: there are multiple sets of data, you need to find out the cut point of each group of data, and output the number of blocks where the cut

Algorithm implementation:

What is a cut point: when a non-connecting graph is stripped of a point and connected to the point, the undirected graph is divided into multiple disjoint sub-blocks, which are called cut points

What is a timestamp: The earliest time to visit when searching

Algorithm: Tarjan algorithm

Maintenance Dfn[u] represents the timestamp of U

Low[u] Represents the time stamp of the earliest ancestor that the U point can return to

Cut[u] Indicates the number of blocks to which the U point belongs

Determine the condition of the cut point Dfn[u]>=low[v]//v Point and its block does not have an edge point above the U point

Cut array Start assignment 1//each point belongs to at least one block

Each judgment cut point condition establishes cut[u]++;

Finally, if cut[u]>=2, you are the cutting point.

Note: The point at which you start the search is that the time stamp is the least, so the condition of the cut must be met, so the initial value is assigned 0.

Storage of graphs: chain-forward stars

1#include <cstdio>2#include <cmath>3#include <cstring>4#include <cstdlib>5#include <queue>6#include <stack>7#include <vector>8#include <iostream>9#include"algorithm"Ten using namespacestd; OnetypedefLong LongLL; A Const intmax1=1005; - Const intMax2=2505; - intn,m; the intTot,c,tx; - intHEAD[MAX1],ADJ[MAX2],NEXT[MAX2]; - intDfn[max1],low[max1],sta[max1]; - BOOLT[max1]; + intCut[max1]; - voidAddedge (intUintv) { +tot++; Aadj[tot]=v; atnext[tot]=Head[u]; -head[u]=tot; - } - voidDfsintXintFA) { -t[x]=true; -sta[++sta[0]]=x; indfn[x]=low[x]=++C; -  inti,j; to  BOOLFlag; +flag=true; -   for(i=head[x];i;i=Next[i]) the{if(Adj[i]==fa &&flag) *{flag=true; $    Continue;Panax Notoginseng   } -   if(T[adj[i]]) thelow[x]=min (Low[x],dfn[adj[i]]); +   Else A {DFS (adj[i],x); thelow[x]=min (Low[x],low[adj[i]]); +    if(low[adj[i]]>=Dfn[x]) -{ while(sta[sta[0]]!=x) ${sta[0]--; $     } -cut[sta[sta[0]]]++; -    } the   } -  }Wuyi } the intMain () { -Freopen ("spf.in","R", stdin); WuFreopen ("Spf.out","W", stdout); -  intI,j;intcas;cas=0; About  intu,v; $   while(1){ -scanf"%d",&u); -  if(u==0) -    Break; Aprintf"Network #%d\n",++CAs); +Memset (Next,0,sizeof(next)); theMemset (Head,0,sizeof(head)); -memset (adj,0,sizeof(adj)); $memset (DFN,0,sizeof(DFN)); thememset (Low,0,sizeof(Low)); thememset (Cut,0,sizeof(cut)); thememset (T,false,sizeof(t)); thetx=sta[0]=c=n=m=0; -   while(1) in{scanf ("%d",&v); them++; then=Max (N,max (u,v)); About Addedge (u,v); the Addedge (v,u); thescanf"%d",&u); the   if(u==0) +     Break; -  } the   for(i=1; i<=n;i++)Bayi   if(!T[i]) the{cut[i]=-1; the DFS (i,i); -   } -  BOOLflag=true; the   for(i=1; i<=n;i++) the   if(cut[i]>0) the{flag=false; theprintf"SPF node%d leaves%d subnets\n", i,cut[i]+1); -   } the  if(flag) puts ("No SPF Nodes"); thePutchar ('\ n'); the  }94  return 0; the } the  

POJ-1523 SPF (Tarjan for cutting points)