HDU 1829 - A Bug's Life

 1 #include <cstdio>
 2 using namespace std;
 3 int f[2000+5],num[2000+5],t,n,m,a,b,fa,fb;
 4 int sf(int x){
 5     if(x==f[x]) return x;
 6     else {
 7         int fx=sf(f[x]);
 8         num[x]=(num[x]+num[f[x]])%2;
 9         return f[x]=fx;
10     }
11 }
12 int main(){
13     scanf("%d",&t);
14     for(int k=1;k<=t;k++){
15         printf("Scenario #%d:\n",k);
16         scanf("%d%d",&n,&m);    bool flag=1;
17         for(int i=0;i<=n;i++) f[i]=i,num[i]=0;
18         for(int i=1;i<=m;i++){
19             scanf("%d%d",&a,&b);
20             if(flag){
21                 fa=sf(a); fb=sf(b); 
22                 if(fa==fb){ if((num[a]-num[b]+2)%2!=1) flag=0;}//避免负数 
23                 else f[fb]=fa,num[fb]=(num[a]-num[b]+1+2)%2;
24             }
25         }
26         if(flag) puts("No suspicious bugs found!\n");
27         else  puts("Suspicious bugs found!\n");
28     } return 0;
29 }