cf786E ALT (最小割+倍增优化建图)

  1 #include<bits/stdc++.h>
  2 #define pa pair<int,int>
  3 #define CLR(a,x) memset(a,x,sizeof(a))
  4 using namespace std;
  5 typedef long long ll;
  6 const int maxn=2e4+10,inf=0x3f3f3f3f;
  7 
  8 inline ll rd(){
  9     ll x=0;char c=getchar();int neg=1;
 10     while(c<‘0‘||c>‘9‘){if(c==‘-‘) neg=-1;c=getchar();}
 11     while(c>=‘0‘&&c<=‘9‘) x=x*10+c-‘0‘,c=getchar();
 12     return x*neg;
 13 }
 14 
 15 struct Edge{
 16     int b,l,ne;
 17 }ek[maxn*100];
 18 int N,M,ekh[maxn*50],kct=1;
 19 int egh[maxn],eg[maxn*2][2],ect=1;
 20 int dep[maxn*40],fa[maxn][20],id[maxn][20],pct=2;
 21 int S=1,T=2,P[maxn];
 22 int A[maxn],cur[maxn*40];
 23 bool flag[maxn*40],B[maxn];
 24 queue<int> q;
 25 
 26 inline void adeg(int a,int b){
 27     eg[++ect][0]=b;eg[ect][1]=egh[a];egh[a]=ect;
 28 }
 29 inline void adek(int a,int b,int c){
 30     // printf("!%d %d %d\n",a,b,c);
 31     ek[++kct].b=b,ek[kct].l=c,ek[kct].ne=ekh[a],ekh[a]=kct; 
 32     ek[++kct].b=a,ek[kct].l=0,ek[kct].ne=ekh[b],ekh[b]=kct; 
 33 }
 34 
 35 void dfs(int x){
 36     for(int i=0;fa[x][i]&&fa[fa[x][i]][i];i++){
 37         fa[x][i+1]=fa[fa[x][i]][i];
 38         id[x][i+1]=++pct;
 39         adek(id[x][i+1],id[x][i],inf);
 40         adek(id[x][i+1],id[fa[x][i]][i],inf);
 41     }
 42     for(int i=egh[x];i;i=eg[i][1]){
 43         int b=eg[i][0];
 44         if(b==fa[x][0]) continue;
 45         fa[b][0]=x;dep[b]=dep[x]+1;
 46         id[b][0]=++pct;adek(id[b][0],T,1);
 47         // printf("~%d %d\n",b,id[b][0]);
 48         dfs(b);
 49     }
 50 }
 51 
 52 void buildlca(int x,int y,int p){
 53     if(dep[x]<dep[y]) swap(x,y);
 54     for(int i=log2(dep[x]-dep[y]);i>=0&&dep[x]!=dep[y];i--){
 55         if(dep[fa[x][i]]>=dep[y]){
 56             adek(p,id[x][i],1);
 57             x=fa[x][i];
 58         }
 59     }
 60     if(x==y) return;
 61     for(int i=log2(dep[x]);i>=0;i--){
 62         if(fa[x][i]!=fa[y][i]){
 63             adek(p,id[x][i],1);adek(p,id[y][i],1);
 64             x=fa[x][i],y=fa[y][i];
 65         }
 66     }
 67     adek(p,id[x][0],1);adek(p,id[y][0],1);
 68         
 69 }
 70 
 71 bool bfs(){
 72     CLR(dep,0);CLR(cur,-1);
 73     dep[S]=1;q.push(S);
 74     while(!q.empty()){
 75         int p=q.front();q.pop();
 76         // printf("!@#%d %d\n",p,dep[p]);
 77         for(int i=ekh[p];i;i=ek[i].ne){
 78             int b=ek[i].b;
 79             if(dep[b]||!ek[i].l) continue;
 80             dep[b]=dep[p]+1;
 81             q.push(b);
 82         }
 83     }
 84     return dep[T];
 85 }
 86  
 87 int dinic(int x,int y){
 88     if(x==T) return y;
 89     int tmp=y;
 90     if(cur[x]==-1) cur[x]=ekh[x];
 91     for(int &i=cur[x];i;i=ek[i].ne){
 92         // printf("%d %d\n",i,cur[x]);
 93         int b=ek[i].b;
 94         if(dep[b]!=dep[x]+1||!ek[i].l) continue;
 95         int re=dinic(b,min(ek[i].l,tmp));
 96         ek[i].l-=re,ek[i^1].l+=re;
 97         tmp-=re;if(!tmp) break;
 98     }return y-tmp;
 99 }
100 
101 void getans(int x){
102     flag[x]=1;
103     for(int i=ekh[x];i;i=ek[i].ne){
104         int b=ek[i].b;
105         if(!ek[i].l) continue;
106         if(!flag[b]) getans(b);
107     }
108 }
109 
110 int main(){
111     // freopen("768E.in","r",stdin);
112     int i,j,k;
113     N=rd(),M=rd();
114     for(i=1;i<N;i++){
115         int a=rd(),b=rd();
116         adeg(a,b);adeg(b,a);
117     }
118     for(i=1;i<=M;i++) P[i]=++pct;
119     dep[1]=1;dfs(1);
120     for(i=1;i<=M;i++){
121         int a=rd(),b=rd();
122         adek(S,P[i],1);
123         buildlca(a,b,P[i]);
124     }
125     int ans=0,a=0,b=0;
126     while(bfs()) ans+=dinic(S,inf);
127     getans(S);
128     for(i=3;i<=M+2;i++)
129         if(!flag[i]) A[++a]=i-2;
130     for(i=2;i<=N;i++)
131         if(flag[id[i][0]]) B[i]=1,b++;
132     printf("%d\n%d ",ans,a);
133     for(i=1;i<=a;i++)
134         printf("%d ",A[i]);
135     printf("\n%d ",b);
136     for(i=1;i<N;i++){
137         int x=eg[i<<1][0],y=eg[i<<1|1][0];
138         if(fa[x][0]!=y) swap(x,y);
139         // printf("!%d %d!\n",x,y);
140         if(B[x]) printf("%d ",i);
141     }
142     
143     return 0;
144 }