[hdu4812]D Tree(点分治)

  1 #pragma comment(linker,"/STACK:102400000,102400000")
  2 #include<cstdio>
  3 #include<cstring>
  4 #include<algorithm>
  5 #include<cstdlib>
  6 #include<iostream>
  7 #include<cmath>
  8 #define maxn 100040
  9 #define maxm 1000500
 10 using namespace std;
 11 typedef long long ll;
 12 const ll mod=1000003;
 13 const ll inf=1ll<<60;
 14 ll n,k,ans,size,s[maxn],f[maxn],path[maxn],cr,val[maxn],inv[maxm],ansl,ansr;
 15 ll head[maxn],cnt,root,pathid[maxn],flag[maxm],mp[maxm],ca;
 16 bool vis[maxn];
 17 struct edge{
 18     ll to,nxt;
 19 }e[maxn<<1];
 20 
 21 void add_edge(ll u,ll v){
 22     e[cnt].to=v;
 23     e[cnt].nxt=head[u];
 24     head[u]=cnt++;
 25 }
 26 
 27 inline ll read(){
 28     char k=0;char ls;ls=getchar();for(;ls<‘0‘||ls>‘9‘;k=ls,ls=getchar());
 29     ll x=0;for(;ls>=‘0‘&&ls<=‘9‘;ls=getchar())x=(x<<3)+(x<<1)+ls-‘0‘;
 30     if(k==‘-‘)x=0-x;return x;
 31 }
 32 
 33 void get_root(ll u,ll fa){//get_root会用到size
 34     s[u]=1;f[u]=0;//f是dp数组
 35     for(ll i=head[u];i!=-1;i=e[i].nxt){
 36         ll v=e[i].to;
 37         if(v==fa||vis[v]) continue;
 38         get_root(v,u);
 39         s[u]+=s[v];
 40         f[u]=max(f[u],s[v]);
 41     }
 42     f[u]=max(f[u],size-s[u]);
 43     root=f[root]>f[u]?u:root;
 44 }
 45 
 46 void get_path_size(ll u,ll fa,ll dis){//同时获取size和depth,size是深度，depth是dis的意思
 47     path[cr]=dis%mod*val[u]%mod;
 48     pathid[cr]=u;
 49     cr++;
 50     s[u]=1;
 51     ll tm=path[cr-1]%mod;
 52     for(ll i=head[u];i!=-1;i=e[i].nxt){
 53         ll v=e[i].to;
 54         if(v==fa||vis[v]) continue;
 55         get_path_size(v,u,tm);
 56         s[u]+=s[v];
 57     }
 58 }
 59 
 60 void getans(ll a,ll b){
 61     if(a>b) swap(a,b);
 62     if(ansl>a) ansl=a,ansr=b;
 63     else if(ansl==a&&ansr>b) ansr=b;
 64 }
 65 
 66 void work(ll u,ll fa){
 67     vis[u]=true;
 68     for(ll i=head[u];i!=-1;i=e[i].nxt){
 69         ll v=e[i].to;
 70         if(v==fa||vis[v]) continue;
 71         cr=0;
 72         get_path_size(v,u,1);
 73         for(ll j=0;j<cr;j++){
 74             if(path[j]*val[u]%mod==k) getans(pathid[j],u);
 75             ll tm=k*inv[path[j]*val[u]%mod]%mod;
 76             if(flag[tm]!=ca) continue;
 77             getans(mp[tm],pathid[j]);
 78         }
 79         for(int j=0;j<cr;j++){
 80             ll tm=path[j];
 81             if(flag[tm]!=ca||mp[tm]>pathid[j]) flag[tm]=ca,mp[tm]=pathid[j];
 82         }
 83     }
 84     ca++;
 85     for(ll i=head[u];i!=-1;i=e[i].nxt){
 86         ll v=e[i].to;
 87         if(vis[v]||v==fa) continue;
 88         size=s[v],root=0;
 89         get_root(v,u);
 90         work(root,u);
 91     }
 92 }
 93 
 94 void init(){
 95     memset(vis,0,sizeof vis);
 96     memset(head,-1,sizeof head);
 97     memset(flag,0,sizeof flag);
 98     ans=cnt=0;
 99     ca=1;
100 }
101 
102 ll mod_pow(ll x,ll n,ll p){
103     ll res=1;
104     while(n){
105         if(n&1) res=res*x%p;
106         x=x*x%p;
107         n>>=1;
108     }
109     return res;
110 }
111 
112 int main(){
113     ll a,b;
114     f[0]=inf;inv[0]=1;
115     for(ll i=1;i<1000003;i++) inv[i]=mod_pow(i,mod-2,mod);
116     while(scanf("%lld%lld",&n,&k)!=EOF){
117         init();
118         for(int i=1;i<=n;i++) val[i]=read()%mod;
119         for(int i=0;i<n-1;i++){
120             a=read(),b=read();
121             add_edge(a,b);
122             add_edge(b,a);
123         }
124         size=n,root=0;
125         get_root(1,-1);
126         ansl=ansr=inf;
127         work(root,-1);
128         if(ansl==inf) printf("No solution\n");
129         else printf("%lld %lld\n",ansl,ansr);
130     }
131     return 0;
132 }