[bzoj4602] [Sdoi2016]齿轮

 1 #include<cstdio>
 2 #include<iostream>
 3 #include<cstring>
 4 #include<cmath>
 5 #include<cstdlib>
 6 #define ld double
 7 using namespace std;
 8 const int maxn=1023,maxm=10023;
 9 const ld eps=1e-8;
10 struct zs{int too,pre;ld v;}e[maxm<<1];int tot,last[maxn];
11 bool u[maxn];
12 ld val[maxn];
13 int i,j,k,n,m,ans;
14 bool flag;
15  
16 int ra,fh;char rx;
17 inline int read(){
18     rx=getchar(),ra=0,fh=1;
19     while((rx<‘0‘||rx>‘9‘)&&rx!=‘-‘)rx=getchar();
20     if(rx==‘-‘)fh=-1,rx=getchar();
21     while(rx>=‘0‘&&rx<=‘9‘)ra*=10,ra+=rx-48,rx=getchar();return ra*fh;
22 }
23 inline void insert(int a,int b,ld c){
24     e[++tot].too=b,e[tot].v=c,e[tot].pre=last[a],last[a]=tot;
25 }
26 void dfs(int x,ld v){
27     if(u[x])return;u[x]=1,val[x]=v;
28     for(int i=last[x];i&&flag;i=e[i].pre)if(!u[e[i].too])dfs(e[i].too,v*e[i].v);
29     else if(fabs(val[e[i].too]-v*e[i].v)>eps)flag=0;
30 }
31 int main(){int a,b,c,d,TT=0;
32     for(int T=read();T;T--){TT++,tot=0,memset(last,0,(n+1)<<2);
33         n=read(),m=read();
34         for(i=1;i<=m;i++)
35             a=read(),b=read(),c=read(),d=read(),
36             insert(a,b,(ld)d/c),insert(b,a,(ld)c/d);
37         flag=1,memset(u,0,n+1);
38         for(i=1;i<=n&&flag;i++)if(!u[i])dfs(i,(ld)1.0);
39         printf("Case #%d: ",TT);
40         puts(flag?"Yes":"No");
41     }
42     return 0;
43 }
44