ZOJ 2588 Burning Bridges（判断割边）

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题目链接：http://acm.zju.edu.cn/onlinejudge/showProblem.do?problemCode=2588

题意：

// tarjan 求割边的个数 

两个岛还可能存在多个桥的情况

#include <iostream>
#include <cstdlib>
#include <cstdio>
#include <cstring>
#include <queue>
#include <algorithm>
const int N = 210;
const int maxn = 10100;
const int maxm = 221010;
const int inf = 1e8;
#define MIN INT_MIN
#define MAX 1e6
#define LL long long
#define init(a) memset(a,0,sizeof(a))
#define FOR(i,a,b) for(int i = a;i<b;i++)
#define max(a,b) (a>b)?(a):(b)
#define min(a,b) (a>b)?(b):(a)
using namespace std;
struct node
{
    int next,v,flag,id;
}edge[maxm];
int DFN[maxn],low[maxn],bnum,bianhao;
int ans[maxn],ge;
int head[maxn];
int st[maxn],en[maxn];
int cmp(const void *a,const void *b)
{
    return *(int *)a - *(int *)b;
}
void initt()
{
    memset(head,0,sizeof(head));
    bnum = 1;
    bianhao = 1;
    init(DFN);init(low);init(ans);
    ge = 0;
    init(st);init(en);
}
void add(int u,int v,int id)
{
    int i;
    for(i = head[u];i!=0;i=edge[i].next)
    {
        if(edge[i].v == v)
            break;
    }
    if(i)
    {
        edge[i].flag = 1;
        return ;
    }
    edge[bnum].v = v;

    edge[bnum].id = id;
    edge[bnum].flag = 0;
    edge[bnum].next = head[u];
    head[u] = bnum++;
}
void tarjan(int s,int father)
{
    DFN[s] = low[s] = bianhao++;
    for(int i = head[s];i!=0;i = edge[i].next)
    {
        if(DFN[edge[i].v]==0)
        {
            tarjan(edge[i].v,s);

                low[s] = min(low[s],low[edge[i].v]);
                if(DFN[s] < low[edge[i].v] && edge[i].flag==0)
                {
                    ans[ge++] = edge[i].id;
                    st[ge-1] = s;
                    en[ge-1] = edge[i].v;
                }
        }
        else if(edge[i].v != father)
        {
            low[s] = min(low[s],DFN[edge[i].v]);
        }
    }
}
int main()
{
    int t,m,n,a,b;
    scanf("%d",&t);
    while(t-- && scanf("%d%d",&n,&m))
    {
        initt();
        FOR(i,1,m+1)
        {
            scanf("%d%d",&a,&b);
            add(a,b,i);
            add(b,a,i);
        }
        tarjan(1,-1);

        printf("%d\n",ge);
        if(ge!=0)
        {
        qsort(ans,ge,sizeof(int),cmp);

        FOR(i,0,ge-1)
        {
            printf("%d ",ans[i]);
        }
            printf("%d\n",ans[ge-1]);
         /*   puts("割边是");
          FOR(i,0,ge)
           {
            printf("%d->%d\n",st[i],en[i]);
           }*/
        }
        if(t)
            cout<<endl;
    }
    return 0;
}

ZOJ 2588 Burning Bridges（判断割边）

标签：style   blog   http   color   os   io   strong   for   文件   

原文地址：http://blog.csdn.net/wjw0130/article/details/38853717