loj2065 「SDOI2016」模式字符串

ref不是太懂

#include <iostream>
#include <cstring>
#include <cstdio>
using namespace std;
typedef unsigned long long ull;
int T, n, m, hea[1000005], cnt, uu, vv, rnd[1000005], rot, siz[1000005];
int tot, sf[1000005], sg[1000005], ff[1000005], gg[1000005];
ull bse[1000005], hs1[1000005], hs2[1000005], ans;
char ss[1000005], tt[1000005];
bool vis[1000005];
struct Edge{
	int too, nxt;
}edge[2000005];
void rn(int &x){
	char ch=getchar();
	x = 0;
	while(ch<'0' || ch>'9')	ch = getchar();
	while(ch>='0' && ch<='9'){
		x = x * 10 + ch - '0';
		ch = getchar();
	}
}
void add_edge(int fro, int too){
	edge[++cnt].nxt = hea[fro];
	edge[cnt].too = too;
	hea[fro] = cnt;
}
void getRoot(int x, int f){
	rnd[x] = 0;
	siz[x] = 1;
	for(int i=hea[x]; i; i=edge[i].nxt){
		int t=edge[i].too;
		if(!vis[t] && t!=f){
			getRoot(t, x);
			siz[x] += siz[t];
			rnd[x] = max(rnd[x], siz[t]);
		}
	}
	rnd[x] = max(rnd[x], tot-siz[x]);
	if(rnd[x]<rnd[rot])	rot = x;
}
int dfs(int x, int f, int d, ull hx){
	siz[x] = 1;
	hx = hx * 131 + ss[x];
	if(hs1[d]==hx){
		ff[(d-1)%m+1]++;
		ans += sg[m-(d-1)%m];
	}
	if(hs2[d]==hx){
		gg[(d-1)%m+1]++;
		ans += sf[m-(d-1)%m];
	}
	int tmp=1;
	for(int i=hea[x]; i; i=edge[i].nxt){
		int t=edge[i].too;
		if(!vis[t] && t!=f){
			siz[x] += siz[t];
			tmp = max(tmp, dfs(t, x, d+1, hx)+1);
		}
	}
	return tmp;
}
void work(int x){
	vis[x] = true;
	sf[1] = sg[1] = 1;
	int tmp=0;
	for(int i=hea[x]; i; i=edge[i].nxt){
		int t=edge[i].too;
		if(!vis[t]){
			int k=min(m, dfs(t, x, 2, ss[x])+1);
			tmp = max(tmp, k);
			for(int j=1; j<=k; j++){
				sf[j] += ff[j];
				sg[j] += gg[j];
				ff[j] = gg[j] = 0;
			}
		}
	}
	for(int i=1; i<=tmp; i++)
		sf[i] = sg[i] = 0;
	for(int i=hea[x]; i; i=edge[i].nxt){
		int t=edge[i].too;
		if(!vis[t]){
			rot = 0;
			tot = siz[t];
			getRoot(t, x);
			work(rot);
		}
	}
}
int main(){
	cin>>T;
	while(T--){
		rn(n); rn(m);
		scanf("%s", ss+1);
		memset(hea, 0, sizeof(int)*(n+1));
		memset(vis, 0, sizeof(bool)*(n+1));
		cnt = ans = rot = 0;
		tot = n;
		for(int i=1; i<n; i++){
			rn(uu); rn(vv);
			add_edge(uu, vv);
			add_edge(vv, uu);
		}
		scanf("%s", tt+1);
		bse[0] = 1;
		for(int i=1; i<=n; i++){
			bse[i] = bse[i-1] * 131;
			hs1[i] = hs1[i-1] + tt[(i-1)%m+1] * bse[i-1];
			hs2[i] = hs2[i-1] + tt[m-(i-1)%m] * bse[i-1];
		}
		rnd[0] = 0x3f3f3f3f;
		getRoot(1, 0);
		work(rot);
		printf("%llu\n", ans);
	}
	return 0;
}