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| #include<cstdio>
#include<algorithm>
#define mp make_pair
#define X first
#define Y second
using namespace std;
const int maxn=200005,maxe=800005;
int n,e,S,T,ds,dt,fa[maxn],top;
pair<int,int> ans[maxn];
int son[maxe],nxt[maxe],lnk[maxn],tot;
inline void add(int x,int y){
son[++tot]=y;nxt[tot]=lnk[x];lnk[x]=tot;
}
inline int getfa(int x) {return fa[x]==x?x:fa[x]=getfa(fa[x]);}
int main(){
scanf("%d%d",&n,&e);
for (int i=1;i<=n;i++) fa[i]=i;
for (int i=1,x,y;i<=e;i++) scanf("%d%d",&x,&y),add(x,y),add(y,x);
scanf("%d%d%d%d",&S,&T,&ds,&dt);
for (int i=1;i<=n;i++)
if (i!=S&&i!=T)
for (int j=lnk[i];j;j=nxt[j])
if (son[j]!=S&&son[j]!=T)
if (getfa(i)!=getfa(son[j])) ans[++top]=mp(i,son[j]),fa[getfa(i)]=getfa(son[j]);
int fs=0,ft=0;
for (int i=1;i<=n;i++)
if (i!=S&&i!=T)
for (int j=lnk[i];j;j=nxt[j])
if (son[j]==S){
if (getfa(i)!=getfa(S)&&fs<ds) ans[++top]=mp(i,S),fa[getfa(i)]=getfa(S),fs++;
}else
if (son[j]==T){
if (getfa(i)!=getfa(T)&&ft<dt) ans[++top]=mp(i,T),fa[getfa(i)]=getfa(T),ft++;
}
for (int j=lnk[S];j;j=nxt[j])
if (son[j]==T&&getfa(S)!=getfa(T)) ans[++top]=mp(S,T),fs++,ft++;
if (fs>ds||ft>dt||top!=n-1) return puts("No"),0;
puts("Yes");
for (int i=1;i<n;i++) printf("%d %d\n",ans[i].X,ans[i].Y);
return 0;
}
|
