挖坑:CF712E
#include<cstdio> #include<cstring> #include<algorithm> #define maxn 1000005 using namespace std; int n,m,tot,sum,root,top,stack[maxn][2],h[maxn],way[maxn*2],Next[maxn*2],w[maxn*2],size[maxn],power_10[maxn],ni[maxn]; long long ans; bool v[maxn]; int read(){ int x=0,f=1;char ch; for(ch=getchar();ch<'0'||ch>'9';ch=getchar())if(ch=='-')f=-1; for(;ch>='0'&&ch<='9';ch=getchar())x=x*10+ch-'0'; return x*f; } struct Hash{ #define mod 555616 int cnt,head[mod],fuck[maxn],val[maxn],num[maxn]; void clear(int x){head[x%mod]=0;} void insert(int x){ for(int i=head[x%mod];i;i=fuck[i])if(val[i]==x){num[i]++;return;} ++cnt;val[cnt]=x;fuck[cnt]=head[x%mod];head[x%mod]=cnt;num[cnt]=1; } int find(int x){ for(int i=head[x%mod];i;i=fuck[i])if(val[i]==x)return num[i]; return 0; } }hash; void insert(int x,int y,int z){way[++tot]=y;Next[tot]=h[x];h[x]=tot;w[tot]=z;} void exgcd(int a,int b,int &x,int &y){ if(b==0){x=1;y=0;return;} int tx,ty;exgcd(b,a%b,tx,ty); x=ty;y=tx-a/b*ty; } int getni(){ int x,y;exgcd(10,m,x,y); x=(x%m+m)%m;return x; } void getroot(int x,int fa){ size[x]=1;int pps=0; for(int j=h[x];j;j=Next[j])if(way[j]!=fa&&!v[way[j]]){ getroot(way[j],x);size[x]+=size[way[j]];pps=max(pps,size[way[j]]); } if(max(pps,sum-size[x])<=sum/2)root=x; } void reverse(){for(int i=1;i<=top/2;i++)swap(stack[i][0],stack[top-i+1][0]),swap(stack[i][1],stack[top-i+1][1]);} void calc(int x,int fa,int len,int num){ ans+=hash.find((1LL*(-num)*ni[len]%m+m)%m); for(int j=h[x];j;j=Next[j])if(way[j]!=fa&&!v[way[j]])calc(way[j],x,len+1,(1LL*num*10+w[j])%m); } void change(int x,int fa,int len,int num,int op){ if(op)hash.insert(num);else hash.clear(num); for(int j=h[x];j;j=Next[j])if(way[j]!=fa&&!v[way[j]])change(way[j],x,len+1,(1LL*w[j]*power_10[len]+num)%m,op); } void calc(int x,int op){ if(op)hash.insert(0); for(int i=1;i<=top;i++)calc(stack[i][0],x,1,stack[i][1]),change(stack[i][0],x,1,stack[i][1],1); if(op)ans+=hash.find(0)-1,hash.clear(0); for(int i=1;i<=top;i++)change(stack[i][0],x,1,stack[i][1],0); } void work(int x,int s){ top=0;v[x]=1; for(int j=h[x];j;j=Next[j])if(!v[way[j]])++top,stack[top][0]=way[j],stack[top][1]=w[j]; calc(x,1);reverse();calc(x,0); for(int j=h[x];j;j=Next[j])if(!v[way[j]]){ sum=size[way[j]]>size[x]?s-size[x]:size[way[j]]; getroot(way[j],x);work(root,sum); } } int main(){ n=read();m=read(); power_10[0]=ni[0]=1; for(int i=1,j=getni();i<=n;i++)power_10[i]=1LL*power_10[i-1]*10%m,ni[i]=1LL*ni[i-1]*j%m; for(int i=1,x,y,z;i<n;i++){ x=read();y=read();z=read()%m; insert(x,y,z);insert(y,x,z); } sum=n;getroot(0,-1);work(root,sum); printf("%lld\n",ans); return 0; }