省选模版复习——主席树

bzoj3653 谈笑风生

dfs序，主席树水过去吧

#include <vector>
#include <cstdio>
#include <cstring>
#include <algorithm>

using namespace std;
#define pb push_back
typedef long long LL;
const int Maxn=300005;
LL sum[Maxn*20],ans;
int stk[Maxn],dep[Maxn],dfn[Maxn],size[Maxn],T[Maxn];
int son[Maxn*20][2],L[Maxn],R[Maxn],fa[Maxn];
int n,q,x,y,k,i,top,tim,st;
bool v[Maxn];
vector <int> e[Maxn];

void dfs(){
  stk[ top=1 ] =1;
  while (top){
  	x = stk[top];
  	if (!v[x]){
  	  dfn[ L[x]=++tim ] = x;
  	  dep[x] = dep[fa[x]]+1;
  	  size[x] = 1;
  	  v[x] = 1;
  	}
  	while (!e[x].empty()){
  	  y = e[x].back();
  	  e[x].pop_back();
  	  if (y==fa[x]) continue;
  	  fa[y] = x;
  	  stk[++top]=y;
  	  break;
  	}
  	if (stk[top]==x){
	  top--; R[x] = tim;
	  if (fa[x]) size[fa[x]] += size[x];
    }
  }
}

void ins(int &q,int p,int l,int r,int pos,LL val){
  q = ++st;
  son[q][0] = son[p][0];
  son[q][1] = son[p][1];
  sum[q] = sum[p]+val;
  if (l==r) return;
  int mid=(l+r)>>1;
  if (pos<=mid) ins(son[q][0],son[p][0],l,mid,pos,val);
    else ins(son[q][1],son[p][1],mid+1,r,pos,val);
}

LL query(int p,int q,int l,int r,int pos){
  if (l>pos) return 0;
  if  (r<=pos) return sum[q]-sum[p];
  int mid=(l+r)>>1;
  return query(son[p][0],son[q][0],l,mid,pos) +
    query(son[p][1],son[q][1],mid+1,r,pos);
}

void init(){
  dfs();
  for (i=1;i<=n;i++)
  	ins(T[i],T[i-1],1,n,dep[dfn[i]],size[dfn[i]]-1);
}

int main(){
  freopen("laugh.in","r",stdin);
  freopen("laugh.out","w",stdout);
  scanf("%d%d",&n,&q);
  for (i=1;i<n;i++){
  	scanf("%d%d",&x,&y);
  	e[x].pb(y); e[y].pb(x);
  }
  init();
  while (q--){
  	scanf("%d%d",&x,&k);
  	if (dep[x]>k) ans = (LL)k*(size[x]-1);
  	  else ans = (LL)(dep[x]-1)*(size[x]-1);
  	ans = ans+query(T[L[x]],T[R[x]],1,n,dep[x]+k);
  	printf("%I64d\n",ans);
  }
  return 0;
}