Archie

树链刨分之后很显然就成了一条一条的链

那么用线段树维护一下就行了

#include<iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>
using namespace std;
int n,m,r,pp;
struct e{
    int to;
    int ne;
    int k;
}ed[200005];
int x,y,z,f;
int p;
int head[100005];
int son[100005];
int dep[100005];
int sd[100005];
int siz[100005];
int top[100005];
int fa[100005];
int dfn[100005];
int rnk[100005];
void add(int f,int to){
    p++;
    ed[p].ne=head[f];
    ed[p].to=to;
    head[f]=p;
}
int tree[400001];
int lazy[400001];
void pushdown(int R,int l,int r){
    if(lazy[R]){
        lazy[R<<1]+=lazy[R];
        lazy[R<<1|1]+=lazy[R];
        int mid= (l+r)>>1;
        tree[R<<1]+=lazy[R]*(mid-l+1)%pp;
        tree[R<<1|1]+=lazy[R]*(r-mid)%pp;
        lazy[R]=0;
    }
}
void pushup(int r){
    tree[r]=tree[r<<1]+tree[r<<1|1]; 
}
void add(int root,int L,int R,int l,int r,int v){
    if(l<=L&&r>=R){
        lazy[root]+=v;
        tree[root]+=(R-L+1)*v%pp;
        return ;
    }
    pushdown(root,L,R);
    int mid=(L+R)>>1;
    if(l<=mid) add(root<<1,L,mid,l,r,v);
    if(r>mid) add(root<<1|1,mid+1,R,l,r,v);
    pushup(root);
}
int query(int root,int L,int R,int l,int r){
    if(l<=L&&r>=R){
        return tree[root];
    }
    int mid=(L+R)>>1,ans=0;
    pushdown(root,L,R);
    ans%=pp;
        if(l<=mid) ans+=query(root<<1,L,mid,l,r)%pp;
        ans%=pp;
        if(r>mid) ans+=query(root<<1|1,mid+1,R,l,r)%pp;
    //pushup(root);
        return ans%pp;
}
void dfs(int no,int f){
    son[no]=-1;
    siz[no]=1;
    fa[no]=f;
    dep[no]=dep[f]+1;

    for(int i=head[no];i;i=ed[i].ne){
        if(ed[i].to==f) continue;
        dfs(ed[i].to,no);
        siz[no]+=siz[ed[i].to];

        if(son[no]==-1||siz[ed[i].to]>siz[son[no]]){
            son[no]=ed[i].to;
        }
    }
}
int cnt;
void dfs2(int no,int to){
//  cout<<no<<" "<<to<<endl; 
    cnt++;
    dfn[no]=cnt;
    top[no]=to;
    rnk[cnt]=no;
    sd[no]=dfn[no];
    if(-1==son[no]) return ;
    dfs2(son[no],to);
        sd[no]=max(sd[no],sd[son[no]]);
    for(int i=head[no];i;i=ed[i].ne){
        if(ed[i].to==fa[no]||ed[i].to==son[no]) continue;
        dfs2(ed[i].to,ed[i].to);
        sd[no]=max(sd[no],sd[ed[i].to]);
    }

}
void work1(){
        while(top[x]!=top[y]){
            if(dep[top[x]]>=dep[top[y]]){ 
            add(1,1,n,dfn[top[x]],dfn[x],z);
                x=fa[top[x]];

            }else{
                add(1,1,n,dfn[top[y]],dfn[y],z);
                y=fa[top[y]];

            }
        } 
        if(dep[x]>dep[y]){
            add(1,1,n,dfn[y],dfn[x],z);
        }else{
            add(1,1,n,dfn[x],dfn[y],z);
        }
} 
void work2(){
    int ans=0;
        while(top[x]!=top[y]){
            if(dep[top[x]]>=dep[top[y]]){ 
                ans+=query(1,1,n,dfn[top[x]],dfn[x])%pp;
                ans%=pp;
                x=fa[top[x]];

            }else{
                ans+=query(1,1,n,dfn[top[y]],dfn[y])%pp;
                ans%=pp;
                y=fa[top[y]];
            }
        } 
        if(dep[x]>dep[y]){
            ans+=query(1,1,n,dfn[y],dfn[x])%pp;
            ans%=pp;
        }else{
            ans+=query(1,1,n,dfn[x],dfn[y])%pp;
            ans%=pp;
        }
        cout<<ans%pp<<endl;
} 
int fr[1000001];
int main(){
    scanf("%d%d%d%d",&n,&m,&r,&pp);
    for(int i=1;i<=n;++i){
        scanf("%d",&fr[i]);
    }
    for(int i=1;i<n;++i){
        scanf("%d%d",&x,&y);
        add(x,y);
        add(y,x);
    } 
    dep[r]=1;
    dfs(r,r);
    dfs2(r,r);
    for(int i=1;i<=n;++i){
        add(1,1,n,dfn[i],dfn[i],fr[i]);
    }
    while(m--){
        scanf("%d",&f);
        if(f==1){
            scanf("%d%d%d",&x,&y,&z);
            z%=pp;
            work1();
        }
        if(f==2){
            scanf("%d%d",&x,&y);
            work2(); 
        }
        if(f==3) {
            scanf("%d%d",&x,&z);
            z%=pp;
            add(1,1,n,dfn[x],sd[x],z);
        }
        if(f==4) {
            scanf("%d",&x);
            cout<<query(1,1,n,dfn[x],sd[x])%pp<<endl;;
        }
    }
    return 0;
}