2-SAT…
1 /************************************************************** 2 Problem: 1823 3 User: zhuohan123 4 Language: C++ 5 Result: Accepted 6 Time:4 ms 7 Memory:1300 kb 8 ****************************************************************/ 9 10 #include <iostream> 11 #include <cstdio> 12 #include <cstring> 13 #include <algorithm> 14 using namespace std; 15 inline int imin(int a,int b){return a<b?a:b;} 16 struct food{int h,m;}f[110]; 17 struct point{int head,wk,dfn,low,instack;}p[210];int pnum; 18 struct edge{int to,next;}g[2100];int gnum; 19 void addedge(int from,int to) 20 { 21 g[++gnum].to=to;g[gnum].next=p[from].head;p[from].head=gnum; 22 } 23 int blocknum,dfsnum; 24 int s[210],sr; 25 void tarjan(int po) 26 { 27 p[po].dfn=p[po].low=++dfsnum; 28 s[++sr]=po;p[po].instack=true; 29 for(int i=p[po].head;i;i=g[i].next) 30 { 31 if(!p[g[i].to].dfn) 32 { 33 tarjan(g[i].to); 34 p[po].low=imin(p[po].low,p[g[i].to].low); 35 } 36 else if(p[g[i].to].instack) 37 p[po].low=imin(p[po].low,p[g[i].to].dfn); 38 } 39 if(p[po].dfn==p[po].low) 40 { 41 blocknum++; 42 while(s[sr]!=po) 43 { 44 p[s[sr]].wk=blocknum; 45 p[s[sr]].instack=false; 46 sr--; 47 } 48 p[s[sr]].wk=blocknum; 49 p[s[sr]].instack=false; 50 sr--; 51 } 52 } 53 int main(int argc, char *argv[]) 54 { 55 int T;scanf("%d",&T); 56 while(T--) 57 { 58 pnum=gnum=blocknum=dfsnum=0; 59 memset(p,0,sizeof p); 60 int n,m;scanf("%d%d",&n,&m); 61 for(int i=1;i<=n;i++)f[i].h=++pnum,f[i].m=++pnum; 62 while(m--) 63 { 64 char str[60]={0};while(!str[0])gets(str); 65 int a=0,b=0,ha,hb,now=0; 66 while(str[now]!='h'&&str[now]!='m')now++; 67 ha=(str[now]=='h'); 68 while(str[now]>'9'||str[now]<'0')now++; 69 while(str[now]>='0'&&str[now]<='9')a=a*10+str[now]-'0',now++; 70 while(str[now]!='h'&&str[now]!='m')now++; 71 hb=(str[now]=='h'); 72 while(str[now]>'9'||str[now]<'0')now++; 73 while(str[now]>='0'&&str[now]<='9')b=b*10+str[now]-'0',now++; 74 if(ha&&hb)addedge(f[a].m,f[b].h),addedge(f[b].m,f[a].h); 75 if(!ha&&hb)addedge(f[a].h,f[b].h),addedge(f[b].m,f[a].m); 76 if(ha&&!hb)addedge(f[a].m,f[b].m),addedge(f[b].h,f[a].h); 77 if(!ha&&!hb)addedge(f[a].h,f[b].m),addedge(f[b].h,f[a].m); 78 } 79 for(int i=1;i<=pnum;i++) 80 if(!p[i].dfn)tarjan(i); 81 bool isgood=true;; 82 for(int i=1;i<=n;i++) 83 if(p[f[i].h].wk==p[f[i].m].wk) 84 isgood=false; 85 if(isgood)puts("GOOD"); 86 else puts("BAD"); 87 } 88 return 0; 89 }