SGU 242 Student's Morning (网络流+打印路径，Dinic)

http://acm.sgu.ru/problem.php?contest=0&problem=242

网络流+打印路径

原点和人建立权为1的边，人和学校建立权为1的边，学校和汇点建权为2的边

最大流是2*k则yes,否则no

顺便附上修改自他人的带各种优化的Dinic模板~

  1 /**
  2 *网络流+打印路径
  3 *原点和人建立权为1的边，学校和汇点建权为2的边
  4 *最大流是2*k则yes,否则no
  5 *
  6 *@Author: xysmlx xiaohai
  7 */
  8 //#pragma comment(linker, "/STACK:102400000,102400000")
  9 #include<cstdio>
 10 #include<iostream>
 11 #include<cstring>
 12 #include<string>
 13 #include<cmath>
 14 #include<set>
 15 #include<list>
 16 #include<map>
 17 #include<iterator>
 18 #include<cstdlib>
 19 #include<vector>
 20 #include<queue>
 21 #include<stack>
 22 #include<algorithm>
 23 #include<functional>
 24 using namespace std;
 25 typedef long long LL;
 26 #define ROUND(x) round(x)
 27 #define FLOOR(x) floor(x)
 28 #define CEIL(x) ceil(x)
 29 const int maxn=510;
 30 const int inf=0x3f3f3f3f;
 31 const LL inf64=0x3f3f3f3f3f3f3f3fLL;
 32 const double INF=1e30;
 33 const double eps=1e-6;
 34 
 35 /**
 36 *最大流：加各种优化的Dinic算法($O(V^2E)$)
 37 *输入：图(链式前向星),n(顶点个数,包含源汇),st(源),ed(汇)
 38 *输出：MaxFlow()(最大流)
 39 */
 40 //const int maxn=0;
 41 const int maxm=50010;
 42 //const int inf=0x3f3f3f3f;
 43 struct Edge
 44 {
 45     int v;
 46     int cap;
 47     int next;
 48 } edge[maxm];
 49 int head[maxn],edgeNum;//需初始化
 50 int n,m,d[maxn],cur[maxn];
 51 int st,ed;
 52 void addSubEdge(int u,int v,int cap)
 53 {
 54     edge[edgeNum].v=v;
 55     edge[edgeNum].cap=cap;
 56     edge[edgeNum].next=head[u];
 57     head[u]=edgeNum++;
 58     cur[u]=head[u];
 59 }
 60 void addEdge(int u,int v,int cap)
 61 {
 62     addSubEdge(u,v,cap);
 63     addSubEdge(v,u,0);//注意加反向0边
 64 }
 65 bool BFS()
 66 {
 67     queue<int> Q;
 68     memset(d, -1, sizeof(d));
 69     Q.push(st);
 70     d[st]=0;
 71     while (!Q.empty())
 72     {
 73         int u=Q.front();
 74         Q.pop();
 75         for(int i=head[u]; i!=-1; i=edge[i].next)
 76         {
 77             int v=edge[i].v;
 78             int cap=edge[i].cap;
 79             if(cap&&d[v]==-1)
 80             {
 81                 Q.push(v);
 82                 d[v]=d[u]+1;
 83                 if(v==ed) return 1;
 84             }
 85         }
 86     }
 87     return false;
 88 }
 89 int Aug(int u, int a)
 90 {
 91     if (u==ed) return a;
 92     int aug=0, delta;
 93     for(int &i=cur[u]; i!=-1; i=edge[i].next)
 94     {
 95         int v=edge[i].v;
 96         int cap=edge[i].cap;
 97         if (cap && d[v]==d[u]+1)
 98         {
 99             delta = Aug(v, min(a,cap));
100             if (delta)
101             {
102                 edge[i].cap -= delta;
103                 edge[i^1].cap += delta;
104                 aug += delta;
105                 if (!(a-=delta)) break;
106             }
107         }
108     }
109     if (!aug) d[u]=-1;
110     return aug;
111 }
112 int MaxFlow()
113 {
114     int flow=0;
115     while (BFS())
116     {
117         memcpy(cur,head,sizeof(int)*(n+1));
118         flow += Aug(st,inf);
119     }
120     return flow;
121 }
122 
123 int N,M;
124 void init()
125 {
126     memset(head,-1,sizeof(head));
127     edgeNum=0;
128     st=0,ed=N+M+1;
129     n=N+M+1;
130 }
131 void input()
132 {
133     for(int i=1;i<=N;i++)
134     {
135         addEdge(st,i,1);
136         int u,v;
137         scanf("%d",&u);
138         for(int j=0;j<u;j++)
139         {
140             scanf("%d",&v);
141             addEdge(i,N+v,1);
142         }
143     }
144     for(int i=1;i<=M;i++) addEdge(N+i,ed,2);
145 }
146 void solve()
147 {
148     int f=MaxFlow();
149     if(f!=2*M)
150     {
151         puts("NO");
152         return;
153     }
154     puts("YES");
155     for(int v=1;v<=M;v++)
156     {
157         printf("2");
158         for(int i=head[N+v];i!=-1;i=edge[i].next)
159         {
160             if((i&1)&&edge[i].cap==1) printf(" %d",edge[i].v);
161         }
162         puts("");
163     }
164 }
165 int main()
166 {
167 //    std::ios_base::sync_with_stdio(false);
168 //    freopen("in.cpp","r",stdin);
169     while(~scanf("%d%d",&N,&M))
170     {
171         init();
172         input();
173         solve();
174     }
175     return 0;
176 }
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posted @ 2013-08-28 22:42  xysmlx  阅读(300)  评论(0)  编辑  收藏  举报