luogu 4427 求和

 1 #include<iostream>
 2 #include<cstdio>
 3 #include<cmath>
 4 #include<cstdlib>
 5 #include<cstring>
 6 #include<algorithm>
 7 #include<queue>
 8 #include<vector>
 9 #define ll long long 
10 #define MAXN 300100
11 #define inf 2139062143
12 #define MOD 998244353
13 using namespace std;
14 inline int read()
15 {
16     int x=0,f=1;char ch=getchar();
17     while(!isdigit(ch)) {if(ch==‘-‘) f=-1;ch=getchar();}
18     while(isdigit(ch)) {x=x*10+ch-‘0‘;ch=getchar();}
19     return x*f;
20 }
21 int n,m,hsh[MAXN],HSH[MAXN],bl[MAXN],sz[MAXN],dep[MAXN],fa[MAXN];
22 int nxt[MAXN<<1],fst[MAXN],to[MAXN<<1],cnt;
23 ll sum[51][MAXN],val[MAXN],res;
24 void add(int u,int v){nxt[++cnt]=fst[u],fst[u]=cnt,to[cnt]=v;}
25 void dfs(int x)
26 {
27     sz[x]=val[x]=1;
28     for(int i=fst[x];i;i=nxt[i])
29     {
30         if(to[i]==fa[x]) continue;
31         dep[to[i]]=dep[x]+1,fa[to[i]]=x;
32         dfs(to[i]);sz[x]+=sz[to[i]];
33     }
34 }
35 void DFS(int x,int anc)
36 {
37     int hvs=0;hsh[x]=++cnt,HSH[cnt]=x,bl[x]=anc;
38     for(int i=fst[x];i;i=nxt[i])
39         if(to[i]!=fa[x]&&sz[to[i]]>sz[hvs])    hvs=to[i];
40     if(!hvs) return ;
41     DFS(hvs,anc);
42     for(int i=fst[x];i;i=nxt[i])
43         if(to[i]!=fa[x]&&to[i]!=hvs) DFS(to[i],to[i]);
44 }
45 int main()
46 {
47     n=read();int a,b,c;
48     for(int i=1;i<n;i++) {a=read(),b=read();add(a,b);add(b,a);}
49     dfs(1);cnt=0;
50     DFS(1,1);
51     for(int i=1;i<=50;i++)
52         for(int j=1;j<=n;j++) (val[j]*=dep[HSH[j]])%=MOD,sum[i][j]=(sum[i][j-1]+val[j])%MOD;
53     m=read();
54     while(m--)
55     {
56         a=read(),b=read(),c=read(),res=0;
57         while(bl[a]!=bl[b])
58         {
59             if(dep[bl[a]]<dep[bl[b]]) swap(a,b);
60             (res+=sum[c][hsh[a]]-sum[c][hsh[bl[a]]-1]+MOD)%=MOD;
61             a=fa[bl[a]];
62         }
63         if(dep[a]>dep[b]) swap(a,b);
64         (res+=sum[c][hsh[b]]-sum[c][hsh[a]-1]+MOD)%=MOD;
65         printf("%lld\n",res);
66     }
67 }