ZOJ 2588-Burning Bridges(割边)
来源:互联网 发布:mac quartus 编辑:程序博客网 时间:2024/06/10 04:16
Burning Bridges
Time Limit: 5 Seconds Memory Limit: 32768 KB
Ferry Kingdom is a nice little country located on N islands that are connected by M bridges. All bridges are very beautiful and are loved by everyone in the kingdom. Of course, the system of bridges is designed in such a way that one can get from any island to any other one.
But recently the great sorrow has come to the kingdom. Ferry Kingdom was conquered by the armies of the great warrior Jordan and he has decided to burn all the bridges that connected the islands. This was a very cruel decision, but the wizards of Jordan have advised him no to do so, because after that his own armies would not be able to get from one island to another. So Jordan decided to burn as many bridges as possible so that is was still possible for his armies to get from any island to any other one.
Now the poor people of Ferry Kingdom wonder what bridges will be burned. Of course, they cannot learn that, because the list of bridges to be burned is kept in great secret. However, one old man said that you can help them to find the set of bridges that certainly will not be burned.
So they came to you and asked for help. Can you do that?
Input
The input contains multiple test cases. The first line of the input is a single integer T (1 <= T <= 20) which is the number of test cases. T test cases follow, each preceded by a single blank line.
The first line of each case contains N and M - the number of islands and bridges in Ferry Kingdom respectively (2 <= N <= 10 000, 1 <= M <= 100 000). Next M lines contain two different integer numbers each and describe bridges. Note that there can be several bridges between a pair of islands.
Output
On the first line of each case print K - the number of bridges that will certainly not be burned. On the second line print K integers - the numbers of these bridges. Bridges are numbered starting from one, as they are given in the input.
Two consecutive cases should be separated by a single blank line. No blank line should be produced after the last test case.
Sample Input
2
6 7
1 2
2 3
2 4
5 4
1 3
4 5
3 6
10 16
2 6
3 7
6 5
5 9
5 4
1 2
9 8
6 4
2 10
3 8
7 9
1 4
2 4
10 5
1 6
6 10
Sample Output
2
3 7
1
4
题目意思:
N个岛,M座桥。烧毁尽可能多的桥,但是要保证岛之间的连通性。
输出不会被烧毁的桥的个数,并且输出这些桥的序号。
解题思路:
求割边。
#include <iostream>#include <cstdio>#include <cstring>#include <cmath>#include <vector>#include <queue>#include <map>#include <algorithm>using namespace std;#define INF 0xfffffff#define maxn 100010using namespace std;struct Node{ int j,tag,id;//j是另一个顶点的序号,tag是重边的数量,id是序号 Node *next;//下一个边结点};int n,m;//顶点数、边数int nid;//输入时边的序号Node mem[maxn];//存储边结点int memp;//mem数组中的序号Node *e[maxn];//邻接表int bridge[maxn];//如果bride[i]=1,则第i+1条边是割边int nbridge;//割边的数目int low[maxn],dfn[maxn];int vis[maxn];//0-未访问,1-已经访问,2-已经访问且已检查邻接顶点int add_edge(Node *e[],int i,int j)//在邻接表中插入边(i,j),如果有重边,则相应边结点tag+1{ Node *p; for(p=e[i]; p!=NULL; p=p->next) if(p->j==j) break; if(p!=NULL)//是重边 { p->tag++; return 0; } p=&mem[memp++]; p->j=j; p->next=e[i]; e[i]=p; p->id=nid; p->tag=0; return 1;}void dfs(int i,int father,int dth)//i-当前搜索的顶点,father-i的父亲节点,dth-搜索深度{ vis[i]=1; dfn[i]=low[i]=dth; Node *p; for(p=e[i]; p!=NULL; p=p->next) { int j=p->j; if(j!=father&&vis[j]==1) low[i]=min(low[i],dfn[j]); if(vis[j]==0)//未访问 { dfs(j,i,dth+1); low[i]=min(low[i],low[j]); if(low[j]>dfn[i]&&!p->tag)//重边不可能是割边 bridge[p->id]=++nbridge; } } vis[i]=2;}int main(){ int i,j,k,t; cin>>t; while(t--) { cin>>n>>m; memp=0; nid=0; memset(e,0,sizeof(e)); for(k=0; k<m; ++k,++nid)//读边存入邻接表 { cin>>i>>j; add_edge(e,i-1,j-1); add_edge(e,j-1,i-1); bridge[nid]=0; } nbridge=0; memset(vis,0,sizeof(vis)); dfs(0,-1,1);//从根结点0开始DFS cout<<nbridge<<endl;//输出割边的信息 for(i=0,k=nbridge; i<m; ++i) if(bridge[i]) { cout<<i+1; if(--k) cout<<" "; } if(nbridge) puts(""); if(t) puts(""); } return 0;}/**26 71 22 32 45 41 34 53 610 162 63 76 55 95 41 29 86 42 103 87 91 42 410 51 66 10**/
- ZOJ 2588-Burning Bridges(割边)
- zoj 2588 Burning Bridges (割边/桥)
- zoj 2588 Burning Bridges 割边求解
- ZOJ 2588 Burning Bridges(判断割边)
- zoj 2588 Burning Bridges(割边模板)
- ZOJ 2588 Burning Bridges 割边的求解
- ZOJ 2588 Burning Bridges(求含重边的无向连通图的割边) - from lanshui_Yang
- Burning Bridges-ZOJ1588(割边求解)
- zoj 2588 Burning Bridges
- zoj 2588 Burning Bridges
- zoj 2588 Burning Bridges
- ZOJ 2588 Burning Bridges
- zoj 2588 Burning Bridges 边联通性
- ZOJ2588 Burning Bridges 割边
- ZOJ 2588 Burning Bridges 求割边
- [桥]zoj 2588 Burning Bridges
- ZOJ 2588 Burning Bridges 求割边
- zoj 2588 Burning Bridges 桥
- hadoop1和hadoop2架构图
- odoo学习方法
- VMWare 网络连接的三种模式(bridged、NAT、host-only)
- PHP Yii开源框架入门学习(四)添加新模块
- 1079: [SCOI2008]着色方案
- ZOJ 2588-Burning Bridges(割边)
- 无穷大常数 【INF】
- #205 Interval Minimum Number
- codeforces 707B - Bakery
- SFM总结(二)
- PAT乙级真题100_害死人不偿命的(3n+1)猜想
- 实现一个复杂动画的界面转场(Swift)
- C++常用刷题模板
- 样式扫描和处理工具 awk (增强的sed、grep、sort、find)