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| #include<cstdio>
#include<vector>
#include<algorithm>
using namespace std;
inline char nc(){
static char buf[100000],*l=buf,*r=buf;
return l==r&&(r=(l=buf)+fread(buf,1,100000,stdin),l==r)?EOF:*l++;
}
inline int red(){
int res=0,f=1;char ch=nc();
while (ch<'0'||'9'<ch) {if (ch=='-') f=-f;ch=nc();}
while ('0'<=ch&&ch<='9') res=res*10+ch-48,ch=nc();
return res*f;
}
inline char fstchar(){
char ch=nc();while (ch<'a'||'z'<ch) ch=nc();
return ch;
}
const int maxn=500005,maxe=500005;
int n,q,s[maxn],num[maxn][26];
struct data{
int dep,id;
data () {}
data (int _x,int _y):dep(_x),id(_y) {}
};
bool ans[maxn];
vector<data> V[maxn];
int tot,son[maxe],nxt[maxe],lnk[maxn];
inline void add(int x,int y){
son[++tot]=y;nxt[tot]=lnk[x];lnk[x]=tot;
}
int dep[maxn],H_son[maxn],wt[maxn];
void getH(int x){
H_son[x]=0;wt[x]=1;
for (int j=lnk[x];j;j=nxt[j]){
dep[son[j]]=dep[x]+1; getH(son[j]); wt[x]+=wt[son[j]];
if (!H_son[x]||wt[H_son[x]]<wt[son[j]]) H_son[x]=son[j];
}
}
bool xH[maxn];
void change(int x,int w){
num[dep[x]][s[x]]+=w;
for (int j=lnk[x];j;j=nxt[j])
if (!xH[son[j]]) change(son[j],w);
}
void dsu(int x,bool keep){
for (int j=lnk[x];j;j=nxt[j])
if (son[j]!=H_son[x]) dsu(son[j],0);
if (H_son[x]) dsu(H_son[x],1),xH[H_son[x]]=1;
change(x,1); xH[H_son[x]]=0;
for (int i=0;i<V[x].size();i++){
int tot=0;
for (int j=1;j<=26;j++)
if (num[V[x][i].dep][j]&1) tot++;
ans[V[x][i].id]=(tot<=1);
}
if (!keep) change(x,-1);
}
int main(){
n=red();q=red();
for (int i=2,fa;i<=n;i++) fa=red(),add(fa,i);
for (int i=1;i<=n;i++) s[i]=fstchar()-'a'+1;
for (int i=1;i<=q;i++){
int x=red(),y=red();
V[x].push_back(data(y,i));
}
dep[1]=1;getH(1);dsu(1,0);
for (int i=1;i<=q;i++) puts(ans[i]?"Yes":"No");
return 0;
}
|
