https://www.luogu.org/problemnew/show/P2973
dp一遍，(f_i=sum_{edge(i,j)}frac{f_j imes(1-frac{P}{Q})}{du_j} + frac{P}{Q})
然后发现有环，高斯消元一遍
（zz到高斯消元都能写错。。。）
#include<bits/stdc++.h>
#define il inline
#define vd void
#define double long double
typedef long long ll;
il int gi(){
int x=0,f=1;
char ch=getchar();
while(!isdigit(ch)){
if(ch=='-')f=-1;
ch=getchar();
}
while(isdigit(ch))x=x*10+ch-'0',ch=getchar();
return x*f;
}
int fir[301],dis[90010],nxt[90010],id,in[301];
il vd link(int a,int b){nxt[++id]=fir[a],fir[a]=id,dis[id]=b;}
#define eps 1e-13
double s[301][302];
int main(){
int n=gi(),m=gi(),p=gi(),q=gi(),a,b;
while(m--)a=gi(),b=gi(),link(a,b),link(b,a),++in[a],++in[b];
for(int i=1;i<=n;++i){
if(i==1)s[i][n+1]=1;
for(int j=fir[i];j;j=nxt[j])
s[i][dis[j]]=(p*1.0/q-1)/(in[dis[j]]);
s[i][i]=1;
}
for(int i=1;i<=n;++i){
int t=i;
for(int j=i;j<=n;++j)if(fabs(s[j][i])>eps){t=j;}
for(int j=1;j<=n+1;++j)std::swap(s[t][j],s[i][j]);
for(int j=i+1;j<=n;++j){
if(fabs(s[j][i])<eps)continue;
for(int k=n+1;k>=i;--k)s[j][k]-=s[i][k]*s[j][i]/s[i][i];
}
}
for(int i=n;i;--i){
for(int j=i+1;j<=n;++j)s[i][n+1]-=s[j][n+1]*s[i][j];
s[i][n+1]/=s[i][i];
}
for(int i=1;i<=n;++i)printf("%.9Lf
",s[i][n+1]*p/q);
return 0;
}