RT，不知为什么这个代码过不了。。

#include<bits/stdc++.h>
using namespace std;
const int E=1e5+10,V=5e4+10;
int v,e,need;
struct Node
{
	int s,t,c,col;
}w[E],b[E],edge[E];
int f[V];
int ans;
int blacksum,whitesum;
int read()
{
    int x=0,f=1;
    char s=getchar();
    while(s<'0'||s>'9')
    {
        if(s=='-')
        f=-f;
        s=getchar();
    }
    while(s>='0'&&s<='9')
    {
        x=x*10+s-48;
        s=getchar();
    }
    return x*f;
}
bool cmp(Node i,Node j)
{
	return i.c<j.c;
}
void modify(int x)//类似于归并
{
	int i=1,j=1,k=1;
	while(i<=whitesum&&j<=blacksum)
	{
		if(w[i].c<=b[j].c+x)
		edge[k++]=w[i++];
		else edge[k++]=b[j++];
	}
	while(i<=whitesum) edge[k++]=w[i++];
	while(j<=blacksum) edge[k++]=b[j++];
}
int get(int x)
{
	return f[x]==x?x:f[x]=get(f[x]);
}
int check(int X)
{
	int res=0,cnt=0;
	for(int i=1;i<=v;i++) f[i]=i;
	for(int i=1;i<=e;i++)
	{
		int x=get(edge[i].s),y=get(edge[i].t);
		if(x==y) continue;
		f[x]=y;
		if(edge[i].col==0) cnt++;
		res+=edge[i].c;
	}
	if(cnt>=need) ans=res;//这里不减去消耗是因为前面赋值的时候就没有算消耗
	return cnt;
}
int main()
{
	int s,t,c,col;
	v=read(),e=read(),need=read();
	for(int i=1;i<=e;i++)
	{
		s=read(),t=read(),c=read(),col=read();
		s++,t++;
		if(col==0)
		{
			whitesum++;//白边分类
			w[whitesum].s=s,w[whitesum].t=t,w[whitesum].c=c,w[whitesum].col=0;
		} 
		else
		{
			blacksum++;//黑边分类
			b[blacksum].s=s,b[blacksum].t=t,b[blacksum].c=c,b[blacksum].col=1;
		}
	}
	sort(b+1,b+blacksum+1,cmp);	
    sort(w+1,w+whitesum+1,cmp);//排序
	int l=-100,r=100,mid;
	while(l<=r)
	{
		mid=l+r>>1;
		modify(mid);//修改
		if(check(mid)>=need)//判断
		r=mid-1;
		else l=mid+1;
	}
	printf("%d",ans);
	return 0;
}