UVA 315 求割点数

题目链接：http://uva.onlinejudge.org/index.php?option=com_onlinejudge&Itemid=8&page=show_problem&problem=251

测模版：

#include <stdio.h>
#include <iostream>
#include <algorithm>
#include <string.h>
#include <queue>
#include <vector>
using namespace std;
#define N 100005
#define M 200300
#define inf 10000000
struct Edge{
	int from,to,next;
	bool cut;
}edge[2*M];
int head[N],edgenum;
int Low[N],DFN[N],Stack[N],Stack2[N];//Belong数组的值是1~block
int Index,top,top2;
int Belong[N],block;//新图的连通块标号（1~block）
bool Instack[N], cut[N];
int bridge; //割桥数量
int add_block[N]; //add_block[i]表示删掉i点后增加的连通分量数
void addedge(int u,int v){
	Edge E={u,v,head[u],0}; edge[edgenum]=E; head[u] = edgenum++;
	Edge E2={v,u,head[v],0};edge[edgenum]=E2;head[v] = edgenum++;
}
void Tarjan(int u,int pre){
	int v, son = 0;
	Low[u] = DFN[u] = ++Index;
	Stack[top++] = u;
	Stack2[top2++] = u;
	Instack[u] = true;
	for(int i = head[u]; ~i ;i = edge[i].next){
		v = edge[i].to;
		// 如果重边有效的话下面这句改成: if(v == pre && pre_num == 0){pre_num++;continue;} pre_num在for上面定义 int pre_num=0;
		if( v == pre )continue;
		if( !DFN[v] )
		{
			son++;
			Tarjan(v,u);
			if(Low[u] > Low[v])Low[u] = Low[v];
			if(Low[v] > Low[u])
			{
				bridge++;
				edge[i].cut = edge[i^1].cut = true;
			}
			if(u != pre && Low[v] >= DFN[u])//不是树根
			{
				cut[u] = true;
				add_block[u]++;
			}
		}
		else if(Low[u] > DFN[v])Low[u] = DFN[v];
	}
	if(Low[u] == DFN[u]){
		block++;
		do{
			v = Stack[--top];
			Instack[v] = false;
			Belong[v] = block;
		}while( v != u );
	}
	if(u == pre && son > 1)cut[u] = true;
	if(u == pre)add_block[u] = son - 1;
	Instack[u] = false;
	top2--;
}
void work(int l, int r){
	memset(DFN,0,sizeof(DFN));
	memset(Instack,false,sizeof(Instack));
	memset(cut, false, sizeof cut);
	Index = top = block = bridge = 0;
	top2 = 0;
	for(int i = l; i <= r; i++)if(!DFN[i])Tarjan(i,i);
}
vector<int>G[N];//点标从1-block
void suodian(){
	for(int i = 1; i <= block; i++)G[i].clear();
	for(int i = 0; i < edgenum; i+=2){
		int u = Belong[edge[i].from], v = Belong[edge[i].to];
		if(u==v)continue;
		G[u].push_back(v), G[v].push_back(u);
	}
}
void init(){edgenum = 0; memset(head,-1,sizeof(head));}

int g[110][110];
char buf[1010];
int main(){
	int n;
	while(scanf("%d",&n),n){
		gets(buf);
		memset(g,0,sizeof(g));
		while(gets(buf))
		{
			if(strcmp(buf,"0")==0)break;
			char *p = strtok(buf," ");
			int u;
			sscanf(p,"%d",&u);
			p = strtok(NULL," ");
			int v;
			while(p)
			{
				sscanf(p,"%d",&v);
				p = strtok(NULL," ");
				g[u][v]=g[v][u]=1;
			}
		}
		init();
		for(int i = 1;i <= n;i++)
			for(int j = i+1;j <= n;j++)
				if(g[i][j])
				{
					addedge(i,j);
				}
				work(1,n);
				int ans = 0;
				for(int i = 1; i <= n; i++)ans += cut[i];
				printf("%d\n",ans);
	}
	return 0;
}

UVA 315 求割点数,码迷,mamicode.com