没写完

code: 

#include <bits/stdc++.h>    
#define N 200004  
#define ll long long  
#define mod 1000000007   
#define setIO(s) freopen(s".in","r",stdin) 
using namespace std;            
struct Lowbit 
{
    ll M[N];           
    int C[N];   
    int lowbit(int t) 
    {
        return t&(-t);
    }       
    void add(int x,int v) 
    {        
        while(x<N)  C[x]+=v, x+=lowbit(x); 
    }  
    void mul(int x,int v) 
    {  
        while(x<N)  M[x]=(ll)M[x]*v%mod,x+=lowbit(x); 
    }       
    int qsum(int x) 
    {
        int re=0; 
        while(x>0)  re+=C[x],x-=lowbit(x);  
        return re;  
    } 
    int qmul(int x)
    {
        ll re=1ll; 
        while(x>0)  re=re*M[x]%mod,x-=lowbit(x);  
        return re;   
    }
    void clr(int x) 
    {
        while(x<N)  M[x]=1,x+=lowbit(x);  
    }
}addv,mulv;         

ll ans=1ll;   
int root,edges,sn,tot;   
int hd[N],to[N<<1],nex[N<<1],col[N<<1],val[N<<1],size[N],mx[N],vis[N];      

void addedge(int u,int v,int vv,int c) 
{
    nex[++edges]=hd[u],hd[u]=edges,to[edges]=v,val[edges]=vv,col[edges]=c;          
}
struct node 
{
    int x,y,op,v;  
    node(int x=0,int y=0,int op=0,int v=0):x(x),y(y),op(op),v(v){}  
}q[N];  
bool cmp(node a,node b) 
{
    return (a.x==b.x&&a.y==b.y)?(a.z>b.z):(a.x==b.x?a.y<b.y:a.x<b.x); 
} 
inline int qpow(int x,int y) 
{
    int re=1; 
    for(;y;y>>=1,x=1ll*x*x%mod)   if(y&1)  re=1ll*re*x%mod;   
    return re;   
}
void getroot(int u,int ff) 
{ 
    size[u]=1,mx[u]=0; 
    for(int i=hd[u];i;i=nex[i]) 
    {
        int v=to[i]; 
        if(v==ff||vis[v])    continue; 
        getroot(v,u); 
        size[u]+=size[v]; 
        mx[u]=max(mx[u],size[v]); 
    } 
    mx[u]=max(mx[u],sn-size[u]); 
    if(mx[u]<mx[root]) root=u; 
}
void dfs(int u,int ff,int x,int y,int v) 
{        
    q[++tot]=node(2*y-x,y-2*x,0,v);           
    q[++tot]=node(x-2*y,2*x-y,1,v);            
    for(int i=hd[u];i;i=nex[i]) 
    {
        int v=to[i];      
        if(v==ff||vis[v])    continue;    
        dfs(v,u,x+(col[i]==0),y+(col[i]==1),1ll*v*val[i]%mod);          
    }  
}
void calc(int u,int flag,int pre,int v) 
{            
    tot=0;  
    dfs(u,0,pre==0,pre==1,v);           
    sort(q+1,q+1+tot,cmp);          
    for(int i=1;i<=tot;++i) 
    {
        if(q[i].op==0) 
        {   
            addv.add(q[i].y,1);               
            mulv.mul(q[i].y,q[i].v);        
        } 
        else 
        {    
            int a1=mulv.qmul(q[i].y);     
            int a2=addv.qsum(q[i].y);    
            int delta=1ll*a1*qpow(q[i].v,a2)%mod;       
            if(flag==-1)   delta=qpow(delta,mod-2);    
            ans=1ll*ans*delta%mod;      
        }
    }                              
    for(int i=1;i<=tot;++i) 
    {
        if(!q[i].op) 
        {
            addv.add(q[i].y,-1);       
            mulv.clr(q[i].y);  
        }
    }      
}
void solve(int u) 
{    
    calc(u,1,-1,1);          
    vis[u]=1;  
    for(int i=hd[u];i;i=nex[i])  
    {
        int v=to[i]; 
        if(vis[v])   continue;   
        calc(v,-1,col[i],val[i]);        
    }   
    for(int i=hd[u];i;i=nex[i]) 
    {
        int v=to[i]; 
        if(vis[v])   continue;   
        sn=size[v],root=0,getroot(v,u),solve(root);   
    }
}
int main() 
{ 
    setIO("input");    
    memset(mulv.M,1,sizeof(mulv.M));           
    int i,j,n;  
    scanf("%d",&n); 
    for(i=1;i<n;++i) 
    {
        int x,y,z,c;         
        scanf("%d%d%d%d",&x,&y,&z,&c);     
        add(x,y,z,c),add(y,x,z,c);  
    }  
    sn=mx[0]=n,getroot(1,0),solve(root);   
    printf("%lld
",ans);   
    return 0; 
}