BZOJ 1782 [Usaco2010 Feb]slowdown 慢慢游 dfs序，树状数组

还是比较水的

用dfs序来维护子树信息，我们让一个点归位后，使这个点所在点的子树加一，然后每次得出答案就行了

#include <iostream>#include <cstdio>#include <cmath>#include <algorithm>#include <queue>#include <string>#include <map>#include <cstring>#include <ctime>#include <vector>#define ll long long#define maxn 2000100#define eps 1e-8#define inf 1e9#define For(i,j,k) for(ll i=j;i<=k;i++)#define Dow(i,j,k) for(ll i=k;i>=j;i--)#define clr(x, c) memset(x, c, sizeof(x))using namespace std;inline ll read(){   ll x=0,f=1;char ch=getchar();   while(ch<'0'||ch>'9'){if(ch=='-')f=-1;ch=getchar();}  while(ch>='0'&&ch<='9'){x=x*10+ch-'0';ch=getchar();}  return x*f; }inline void write(ll x){    if (x<0) putchar('-'),x=-x; if (x>=10) write(x/10);   putchar(x%10+'0');  }inline void writeln(ll x){write(x);puts("");};int poi[300001],nxt[300001],f[300001],F[300001],n,x,y,p[300001],cnt,ans[300001];bool vis[300001];inline void add(int x,int y){poi[++cnt]=y;nxt[cnt]=f[x];f[x]=cnt;}inline int lowbit(int x){return x&-x;}inline void ADD(int x,int v){for(;x<=n;x+=lowbit(x)) F[x]+=v;}inline int get(int x){int sum=0;for(;x;x-=lowbit(x))    sum+=F[x];return sum;}inline void dfs(int x){    vis[x]=1;    ans[p[x]]=get(p[x]);    ADD(p[x],1);    for(int i=f[x];i;i=nxt[i])        if(!vis[poi[i]])    dfs(poi[i]);    ADD(p[x],-1);}int main(){    n=read();    For(i,1,n-1)        x=read(),y=read(),add(x,y),add(y,x);    For(i,1,n)  x=read(),p[x]=i;        dfs(1);    For(i,1,n)  writeln(ans[i]);}