BZOJ 4568 幸运数字

#include<iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>
#include<cstdlib>
#define maxv 20050
#define maxe 40050
using namespace std;
long long n,q,w[maxv],nume=0,g[maxv],x,y,anc[maxv][16],dis[maxv],fath[maxv];
long long regis[65],table[65];
long long k1[65],k2[65];
struct edge
{
    long long v,nxt;
}e[maxe];
struct base
{
    long long ins[65];
}r[maxv][16];
void gettable()
{
    table[0]=1;
    for (int i=1;i<=60;i++)
        table[i]=table[i-1]<<1;
}
void clear()
{
    for (int i=0;i<=15;i++)
        for (int j=0;j<=60;j++)
            r[0][i].ins[j]=0;
}
void addedge(long long u,long long v)
{
    e[++nume].v=v;
    e[nume].nxt=g[u];
    g[u]=nume;
}
void dfs(long long x,long long father)
{
    anc[x][0]=x;fath[x]=father;dis[x]=dis[father]+1;
    for (long long i=60;i>=0;i--)
    {
        if (w[x]&table[i])
        {
            r[x][0].ins[i]=w[x];
            break;
        }
    }
    for (long long i=g[x];i;i=e[i].nxt)
    {
        long long v=e[i].v;
        if (v!=father)
            dfs(v,x);
    }
}
void add(long long x,long long a,long long y,long long b)
{
    memset(k1,0,sizeof(k1));
    memset(k2,0,sizeof(k2));
    int flag=1;
    for (int i=0;i<=60;i++)
    {
        k1[i]=r[x][a].ins[i];
        k2[i]=r[y][b].ins[i];
        if (!regis[i]) flag=0;
    }
    if (flag==1) return;
    for (long long i=0;i<=60;i++)
    {
        if (k1[i])
        {
            for (long long j=60;j>=0;j--)
            {
                if (k1[i]&table[j])
                {
                    if (!regis[j]) {regis[j]=k1[i];break;}
                    else k1[i]^=regis[j];
                }
            }
        }
        if (k2[i])
        {
            for (long long j=60;j>=0;j--)
            {
                if (k2[i]&table[j])
                {
                    if (!regis[j]) {regis[j]=k2[i];break;}
                    else k2[i]^=regis[j];
                }
            }
        }
    }
}
long long lca(long long x,long long y)
{
    if (dis[x]<dis[y]) swap(x,y);
    for (long long e=15;e>=0;e--)
    {
        if (dis[fath[anc[x][e]]]>=dis[y])
            x=fath[anc[x][e]];
    }
    if (x==y) return x;
    for (long long e=15;e>=0;e--)
    {
        if (fath[anc[x][e]]!=fath[anc[y][e]])
        {
            x=fath[anc[x][e]];
            y=fath[anc[y][e]];
        }
    }
    return fath[x];
}
void work()
{
    memset(regis,0,sizeof(regis));
    long long t=lca(x,y);
    for (long long e=15;e>=0;e--)    
    {
        if (dis[fath[anc[x][e]]]>=dis[t])
        {
            add(x,e,0,0);
            x=fath[anc[x][e]];
        }
    }
    for (long long e=15;e>=0;e--)
    {
        if (dis[fath[anc[y][e]]]>=dis[t])
        {
            add(y,e,0,0);
            y=fath[anc[y][e]];
        }
    }
    add(t,0,0,0);
    long long ans=0;
    for (long long i=60;i>=0;i--)
    {
        if ((ans^regis[i])>ans)
            ans^=regis[i];
    }
    printf("%lld\n",ans);
}
int main()
{
    gettable();
    scanf("%lld%lld",&n,&q);
    for (long long i=1;i<=n;i++)
        scanf("%lld",&w[i]);
    for (long long i=1;i<=n-1;i++)
    {
        scanf("%lld%lld",&x,&y);
        addedge(x,y);
        addedge(y,x);
    }
    dfs(1,0);
    clear();
    for (long long e=1;e<=15;e++)
    {
        for (long long i=1;i<=n;i++)
        {
            anc[i][e]=anc[fath[anc[i][e-1]]][e-1];
            memset(regis,0,sizeof(regis));
            add(i,e-1,fath[anc[i][e-1]],e-1);
            for (long long j=0;j<=60;j++)
                r[i][e].ins[j]=regis[j];
        }
    }
    for (long long i=1;i<=q;i++)
    {
        scanf("%lld%lld",&x,&y);
        work();
    }
    return 0;
}