萌新刚学OI,0pts请求DEBUG

#include<bits/stdc++.h>
#define MAXN 500005
#define HASH1 31
#define HASH2 29
#define MOD 19260817
#define ADD 131 
using namespace std;
typedef unsigned long long ull; 
int len;
char s[MAXN];
ull base1[MAXN],pre1[MAXN],suf1[MAXN];
ull base2[MAXN],pre2[MAXN],suf2[MAXN];
inline ull get_pre1(int l,int r){
	return ((pre1[r]-pre1[l-1]*base1[r-l+1])%MOD+MOD)%MOD;
}
inline ull get_suf1(int l,int r){
	return ((suf1[l]-suf1[r+1]*base1[r-l+1])%MOD+MOD)%MOD;
}
inline ull get_pre2(int l,int r){
	return ((pre2[r]-pre2[l-1]*base2[r-l+1])%MOD+MOD)%MOD;
}
inline ull get_suf2(int l,int r){
	return ((suf2[l]-suf2[r+1]*base2[r-l+1])%MOD+MOD)%MOD;
}
int main(){
	scanf("%d %s",&len,s+1);
	base1[0]=base2[0]=1;
	for(int i=1;i<=len;++i){
		base1[i]=(base1[i-1]*HASH1)%MOD;
		base2[i]=(base2[i-1]*HASH2)%MOD;
		pre1[i]=(pre1[i-1]*HASH1+(s[i]-'0'+ADD))%MOD;
		pre2[i]=(pre2[i-1]*HASH2+(s[i]-'0'+ADD))%MOD;
	}
	for(int i=len;i>=1;--i){
		suf1[i]=(suf1[i+1]*HASH1+('1'-s[i]+ADD))%MOD;
		suf2[i]=(suf2[i+1]*HASH2+('1'-s[i]+ADD))%MOD;
	}
	ull ans=0;
	for(int i=1;i<len;++i){
		int l=0,r=min(i,len-i),res=0;
		if(s[i]==s[i+1]){
			continue;
		}
		while(l<=r){ 
			int mid=(l+r)>>1;
			if(get_pre1(i-mid,i)==get_suf1(i+1,i+1+mid)&&get_pre2(i-mid,i)==get_suf2(i+1,i+1+mid)){
				l=mid+1;
				res=l;
			}else{
				r=mid-1;
			}
		}
		ans+=res;
	}
	printf("%llu",ans);
	return 0;
}