翻了很多同样结果的代码, 都是直接从父节点找trans导致的, 但蒟蒻的代码应该没有这个问题,求各位dalao帮忙看看orz

#include<cstdio>
#include<iostream>
#include<cstring>
using namespace std;
typedef long long LL;
const int MAX = 500000 + 10;

class PAM {
public:	
	int len; 
	PAM* fail; 
	PAM* trans;
	PAM* ch[30];

	void Init(int, PAM*, PAM*); 
	void New(int,int);
	PAM* Gf(int); 
	PAM* Gt(int,int);
	
}*Ev, *Od, *last;

char s[MAX];
int t, k, Index, ans;

int main() { /**/
	Ev = new PAM; Od = new PAM; //Ev偶根 Od奇根 
	Ev->Init(0, Od, Ev);  Od->Init(-1, Ev, Ev);  
	last = Ev;
	
	cin>>t;
	cin>>s+1;
	t = strlen(s+1);
	
	for(int i = 1; i <= t; i++) {
		int T = s[i] - 'a';
		last = last->Gf(i);	 
		
		if(last->ch[T] == Ev) last->New(T,i);
		last = last->ch[T];
		
		if(last->len % 4 == 0 and last->trans->len == last->len/2) ans = max(ans, last->len);
	}
	printf("%d", ans);	
	return 0;
} /**/

void PAM::Init(int k, PAM* to, PAM* z) { //初始化, 
	len = k; fail = to; trans = fail; //trans默认为fail 
	for(int i = 0; i < 30; i++) ch[i] = z; 
}
void PAM::New(int k, int pos) { //新建节点 
	PAM* Tch = new PAM;
	Tch->Init(len+2, fail->Gf(pos)->ch[k], Ev); //初始化  len和 fail , trans默认为fail 

	if(Tch->len > 2) Tch->trans = trans->Gt(pos, Tch->len)->ch[k];  //如果新节点长度大于2, 从他的父亲(即last)的trans开始跳 
	ch[k] = Tch;	
}
PAM* PAM::Gf(int pos) { return s[pos-len-1] == s[pos] ? this : fail->Gf(pos); } //跳fail 
PAM* PAM::Gt(int pos, int now) { return s[pos-len-1] != s[pos] or (len + 2) * 2 > now ? fail->Gt(pos, now) : this; } //跳trans