BZOJ 2819 Nim

#include<iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>
#define maxv 500500
#define maxe 1000500
using namespace std;
struct edge
{
    int v,nxt;
}e[maxe];
char type[5];
int n,c[maxv],x,y,nume=0,g[maxv],m;
int fath[maxv],size[maxv],dis[maxv],top[maxv],w[maxv],son[maxv],cnt=0,fw[maxv];
int ls[maxv<<2],rs[maxv<<2],val[maxv<<2],tot=0,root;
void addedge(int u,int v)
{
    e[++nume].v=v;
    e[nume].nxt=g[u];
    g[u]=nume;
}
void dfs1(int x)
{
    size[x]=1;son[x]=0;
    for (int i=g[x];i;i=e[i].nxt)
    {
        int v=e[i].v;
        if (v!=fath[x])
        {
            dis[v]=dis[x]+1;fath[v]=x;
            dfs1(v);
            size[x]+=size[v];if (size[v]>size[son[x]]) son[x]=v;
        }
    }
}
void dfs2(int x)
{
    if (son[fath[x]]==x) top[x]=top[fath[x]];else top[x]=x;
    w[x]=++cnt;fw[cnt]=x;
    if (son[x]!=0) dfs2(son[x]);
    for (int i=g[x];i;i=e[i].nxt)
    {
        int v=e[i].v;
        if ((v!=fath[x]) && (v!=son[x]))
            dfs2(v);
    }
}
void build(int &now,int left,int right)
{
    now=++tot;
    if (left==right)
    {
        val[now]=c[fw[left]];
        return;
    }
    int mid=(left+right)>>1;
    build(ls[now],left,mid);
    build(rs[now],mid+1,right);
    val[now]=val[ls[now]]^val[rs[now]];
}
void modify(int now,int left,int right,int pos,int x)
{
    if ((left==right) && (left==pos))
    {
        val[now]=c[fw[left]];
        return;
    }
    int mid=(left+right)>>1;
    if (pos<=mid) modify(ls[now],left,mid,pos,x);
    else modify(rs[now],mid+1,right,pos,x);
    val[now]=val[ls[now]]^val[rs[now]];
}
int ask(int now,int left,int right,int l,int r)
{
    if ((left==l) && (right==r))
        return val[now];
    int mid=(left+right)>>1;
    if (r<=mid) return ask(ls[now],left,mid,l,r);
    else if (l>=mid+1) return ask(rs[now],mid+1,right,l,r);
    else return ask(ls[now],left,mid,l,mid)^ask(rs[now],mid+1,right,mid+1,r);
}
void work()
{
    scanf("%d%d",&x,&y);
    int f1=top[x],f2=top[y];
    int now=0;
    while (f1!=f2)
    {
        if (dis[f1]<dis[f2]) {swap(f1,f2);swap(x,y);}
        now^=ask(root,1,cnt,w[f1],w[x]);
        x=fath[f1];f1=top[x];
    }
    if (dis[x]>dis[y]) swap(x,y);
    now^=ask(root,1,cnt,w[x],w[y]);
    if (now==0) printf("No\n");
    else printf("Yes\n");
}
int main()
{
    scanf("%d",&n);
    for (int i=1;i<=n;i++) scanf("%d",&c[i]);
    for (int i=1;i<=n-1;i++) 
    {
        scanf("%d%d",&x,&y);
        addedge(x,y);
        addedge(y,x);
    }    
    dfs1(1);
    dfs2(1);
    build(root,1,cnt);
    scanf("%d",&m);
    for (int i=1;i<=m;i++)
    {
        scanf("%s",type);
        if (type[0]==‘C‘)
        {
            scanf("%d%d",&x,&y);
            c[x]=y;
            modify(root,1,cnt,w[x],y);
        }
        else work();
    }
    return 0;
}