优雅的字符串哈希写法

如果有CE, 显卡看是不是NT写错模数

using ll = long long;
using ull = unsigned long long;
template<typename hst,hst B,hst M>
struct hash_s{
	static hst phs[N];
	int len ; hst val;
	hash_s(int len_ = 0, hst val_= 0) : len(len_), val(val_){}
	static void init(){
		phs[0] = 1;
		for(int i = 1; i < N; ++i) phs[i] = phs[i - 1] * B % M;
	}
	hash_s friend operator + (const hash_s& x,const hash_s& y){
		return {x.len + y.len, (x.val * phs[y.len] + y.val) % M};
	}
	friend hash_s operator - (const hash_s& x, const hash_s& y){
		return {x.len - y.len, ((x.val - y.val * phs[x.len - y.len]) % M + M) % M};
	}
	friend bool operator == (const hash_s& x, const hash_s& y){
		return x.len == y.len && x.val == y.val;
	}
};
template<typename hst,hst B,hst M>
hst hash_s<hst, B, M>::phs[N];
struct hash_m{
	using _ht1 = hash_s<ll, 131, 998244353>;
	using _ht2 = hash_s<ll, 1145141, 998244853>;
	_ht1 h1;
	_ht2 h2;
	hash_m() = default;
	hash_m(int len_, int val_){
		h1 = {len_, val_};
		h2 = {len_, val_};
	}
	hash_m(_ht1 h1_, _ht2 h2_){
		h1 = h1_;
		h2 = h2_;
	}
	static void init(){
		_ht1::init();
		_ht2::init();
	}
	hash_m friend operator +(const hash_m& x, const hash_m& y){
		return {x.h1 + y.h1, x.h2 + y.h2};
	}
	hash_m friend operator -(const hash_m& x, const hash_m& y){
		return {x.h1 - y.h1, x.h2 - y.h2};
	}
	bool friend operator ==(const hash_m& x, const hash_m& y){
		return x.h1 == y.h1 && x.h2 == y.h2;
	}
};