Vijos1986

树链剖分

#include<cstdio>
#include<cctype>
#include<algorithm>
#define maxn 100002
#define maxm 200002
using namespace std;
int n,m,ne,res,val[maxn],f[maxn],dep[maxn],id[maxn],cnt,siz[maxn],top[maxn],son[maxn],fa[maxn];
int to[2*maxm],nex[2*maxm],head[maxn],tr[maxn<<2];

inline void read(int &x){
    char ch=getchar();x=0;
    while(!isdigit(ch))ch=getchar();
    while(isdigit(ch)){x=(x<<1)+(x<<3)+ch-'0';ch=getchar();}
}

inline void dfs1(int x,int f,int depth){
    dep[x]=depth;fa[x]=f;siz[x]=1;
    int maxson=-1;
    for(int i=head[x];i;i=nex[i]){
        int y=to[i];
        if(y==f)continue;
        dfs1(y,x,depth+1);
        siz[x]+=siz[y];
        if(siz[y]>maxson){son[x]=y;maxson=siz[y];}
    }
}

inline void dfs2(int x,int topf){
    id[x]=++cnt;
    f[cnt]=val[x];
    top[x]=topf;
    if(!son[x])return;
    dfs2(son[x],topf);
    for(int i=head[x];i;i=nex[i]){
        int y=to[i];
        if(y==fa[x]||y==son[x])continue;
        dfs2(y,y);
    }
}

inline void buildtr(int now,int l,int r){
    if(l==r){tr[now]=f[l];return;}
    int mid=(l+r)>>1;
    buildtr(now<<1,l,mid);buildtr(now<<1|1,mid+1,r);
    tr[now]=tr[now<<1]+tr[now<<1|1];
}

inline void updata(int now,int l,int r,int x,int w){
    if(l==r){tr[now]=w;return;}
    int mid=(l+r)>>1;
    if(mid>=x)updata(now<<1,l,mid,x,w);else updata(now<<1|1,mid+1,r,x,w);
    tr[now]=tr[now<<1]+tr[now<<1|1];
}

inline void query(int rt,int l,int r,int L,int R){
    if(l>=L&&r<=R){res+=tr[rt];return;}
    int mid=(l+r)>>1;
    if(mid>=L)query(rt<<1,l,mid,L,R);if(mid<R)query(rt<<1|1,mid+1,r,L,R);
}

inline int qquery(int x,int y){
    int ans=0;
    while(top[x]!=top[y]){
        if(dep[top[x]]<dep[top[y]])swap(x,y);
        res=0;query(1,1,n,id[top[x]],id[x]);
        ans+=res;x=fa[top[x]];
    }
    if(dep[x]>dep[y])swap(x,y);
    res=0;
    query(1,1,n,id[x],id[y]);
    ans+=res;
    return ans;
}

int main(){
    read(n);
    for(int i=1;i<=n;i++)read(val[i]);
    for(int i=1;i<n;i++){
        int u,v;read(u);read(v);
        to[++ne]=v;nex[ne]=head[u];head[u]=ne;
        to[++ne]=u;nex[ne]=head[v];head[v]=ne;
    }
    dfs1(1,0,1);dfs2(1,1);buildtr(1,1,n);
    read(m);
    for(int i=1;i<=m;i++){
        char ch=getchar();while(ch!='Q'&&ch!='C')ch=getchar();
        int u,v;read(u);read(v);
        if(ch=='Q')printf("%d\n",qquery(u,v));else updata(1,1,n,id[u],v);
    }
}