116 lines
2.6 KiB
C++
116 lines
2.6 KiB
C++
#include <iostream>
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#include <cstdio>
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#include <cstring>
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#include <algorithm>
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using namespace std;
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const int MAXN=111111;
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struct Edge{
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int from,to,next;
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Edge(){}
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Edge(int f,int t,int n):from(f),to(t),next(n){}
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}edge[MAXN*2];
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int head[MAXN],tot,fa[MAXN][20],dep[MAXN],q[MAXN],n,m;
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bool vis[MAXN];
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struct Qes{
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int u,v,lca;
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Qes(){}
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Qes(int _u,int _v,int _fa):u(_u),v(_v),lca(_fa){}
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bool operator<(const Qes&rhs)const{
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return dep[lca]>dep[rhs.lca];
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}
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}qes[MAXN];
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void init(){
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for(int i=1;i<=n;i++){
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head[i]=-1;
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vis[i]=0;
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}
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tot=0;
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}
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void add(int f,int t){
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edge[tot]=Edge(f,t,head[f]);
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head[f]=tot++;
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}
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void bfs(int root){
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int tail=0;
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q[tail++]=root;
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fa[root][0]=root;dep[root]=0;
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for(int i=0;i<tail;i++){
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int u=q[i];
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for(int i=1;i<20;i++) fa[u][i]=fa[fa[u][i-1]][i-1];
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for(int i=head[u];~i;i=edge[i].next){
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int v=edge[i].to;
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if(v==fa[u][0])continue;
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fa[v][0]=u;dep[v]=dep[u]+1;
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q[tail++]=v;
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}
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}
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}
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int Lca(int x,int y){
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if(dep[x]<dep[y]){int t=x;x=y;y=t;}
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for(int i=19;~i;i--) if((dep[x]-dep[y])&(1<<i))x=fa[x][i];
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if(x==y)return x;
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for(int i=19;~i;i--) if(fa[x][i]!=fa[y][i]){x=fa[x][i],y=fa[y][i];}
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return fa[x][0];
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}
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bool can(int u,int v,int lca){
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if(vis[u]||vis[v]||vis[lca]) return false;
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for(;u!=lca;u=fa[u][0])
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if(vis[u]) return false;
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for(;v!=lca;v=fa[v][0])
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if(vis[v]) return false;
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return true;
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}
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void cut(int u,int v,int lca){
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for(;u!=lca;u=fa[u][0])
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vis[u]=1;
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for(;v!=lca;v=fa[v][0])
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vis[v]=1;
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vis[lca]=1;
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}
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inline bool get(int &a){
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char c=0;
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a=0;
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do{
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c=getchar();
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}while(c!=EOF && (c<'0'||c>'9'));
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if(c==EOF)return false;
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while('0'<=c && c<='9'){a=a*10-'0'+c;c=getchar();}
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return true;
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}
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inline void ot(int a){
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if(a>9)
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ot(a/10);
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putchar(a%10+'0');
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}
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int main()
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{
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while(get(n)){
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get(m);
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init();
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int u,v;
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for(int i=1;i<n;i++){
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get(u);
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get(v);
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add(u,v);
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add(v,u);
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}
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bfs(1);
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for(int i=0;i<m;i++){
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get(u);
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get(v);
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qes[i]=Qes(u,v,Lca(u,v));
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}
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sort(qes,qes+m);
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int ans=0;
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for(int i=0;i<m;i++){
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if(can(qes[i].u,qes[i].v,qes[i].lca)){
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cut(qes[i].u,qes[i].v,qes[i].lca);
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ans++;
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}
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}
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ot(ans);
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putchar('\n');
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}
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return 0;
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}
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