【2-SAT（两次DFS版）】BZOJ1823-[JSOI2010]满汉全席

 1 #include<iostream>
 2 #include<cstdio>
 3 #include<cstring>
 4 #include<algorithm>
 5 #include<vector>
 6 using namespace std;
 7 const int MAXN=200+50;
 8 vector<int> E[MAXN];
 9 vector<int> rE[MAXN];
10 vector<int> vs;
11 int cmp[MAXN],vis[MAXN];
12 int cnt,n,m;
13 
14 void addedge(int u,int v)
15 {
16     E[u].push_back(v);
17     rE[v].push_back(u); 
18 }
19 
20 void dfs(int u)
21 {
22     vis[u]=1;
23     for (int i=0;i<E[u].size();i++)
24     {
25         int v=E[u][i];
26         if (!vis[v]) dfs(v);
27     }
28     vs.push_back(u);
29 }
30 
31 void rdfs(int u,int t)
32 {
33     vis[u]=1;
34     cmp[u]=t;
35     for (int i=0;i<rE[u].size();i++)
36     {
37         int v=rE[u][i];
38         if (!vis[v]) rdfs(v,t);
39     }
40 }
41 
42 void init()
43 {
44     for (int i=0;i<MAXN;i++) vector<int>().swap(E[i]);
45     for (int i=0;i<MAXN;i++) vector<int>().swap(rE[i]);
46     scanf("%d%d",&n,&m);
47     for (int i=0;i<m;i++)
48     {
49         char c1,c2;
50         int x,y,fx,fy;
51         getchar();
52         scanf("%c%d %c%d",&c1,&x,&c2,&y);
53         if (c1==‘m‘) fx=x+n;else fx=x;
54         if (c2==‘m‘) fy=y+n;else fy=y;
55         if (c1==‘h‘) addedge(x+n,fy);else if (c1==‘m‘) addedge(x,fy);
56         if (c2==‘h‘) addedge(y+n,fx);else if (c1==‘m‘) addedge(y,fx);
57     }
58 }
59 
60 void solve()
61 {
62     memset(vis,0,sizeof(vis));
63     for (int i=1;i<=n;i++) if (!vis[i]) dfs(i);
64     memset(vis,0,sizeof(vis)),cnt=0;
65     for (int i=vs.size()-1;i>=0;i--)
66         if (!vis[vs[i]]) rdfs(vs[i],++cnt);
67 }
68 
69 void get_ans()
70 {
71     for (int i=1;i<=n;i++)
72         if (cmp[i]==cmp[i+n])
73         {
74             puts("BAD");
75             return;
76         }
77     puts("GOOD");
78 } 
79 
80 int main()
81 {
82     int T;
83     scanf("%d",&T);
84     while (T--)
85     {
86         init();
87         solve();
88         get_ans();
89     }
90     return 0;
91 }