daolao求调

#include <bits/stdc++.h>
#define MAXN 2000005
using namespace std;

string s;
char str[MAXN];
int m[MAXN],w[MAXN];
int ln,rn,maxn = -1;

bool check(char x){
	if ((x>='a'&&x<='z')||(x>='A'&&x<='Z')) return 0;
	return 1;
}

void manachar(){
	int id,i;
	for (i=0,id=0;id<=s.length();i++){
		if (i%2==0){
			str[i] = '#';
		}
		else{
			while (check(s[id])) id++;
			if (id<=s.length()){
			    w[i] = id;
				str[i] = tolower(s[id++]);
			}
		}
	}
	int len = i;
	int d = -1,c = -1;
	for (int i=0;i<len;i++){
		int l,r;
		if (d>i){
			if (2*c-i>-1)  m[i] = min(m[2*c-i],d-i);
			else m[i] = d-i;
		}
		else m[i] = 1;
		while (i+m[i]<len&&i-m[i]>-1){
			if (str[i+m[i]]==str[i-m[i]]){
				if (str[i-m[i]]!='#' && w[i-m[i]]!=0){	
					l = i-m[i];
				}
				if (str[i+m[i]]!='#' && w[i+m[i]]!=0){	
					r = i+m[i];
				}
				m[i]++;
		}
			else break;
		}
		if (i+m[i]>d){
			d = i+m[i];
			c = i;
		}
		if (m[i]>maxn){
			maxn = m[i];
			ln = l;
			rn = r;
		}
	}
}

int main(){
	ios::sync_with_stdio(0);cin.tie(0);cout.tie(0);
	getline(cin,s);
	manachar();
	cout << maxn-1 << endl;
	for (int i=w[ln];i<=w[rn];i++) cout << s[i];
	
	return 0;
}