manacher最长回文子串

https://www.luogu.org/blog/codesonic/manacheralgorithm

先放上洛谷的链接，毕竟讲的真好

两道例题

luogu4555 SP7586

inline void change() {
    s[]=s[]='#';
    for(int i=; i<n; i++) {
        s[i*+]=a[i];
        s[i*+]='#';
    }
    n=n*+;
    s[n]=;
}
//替换新串 

inline void manacher() {
    int maxright=,mid;
    for(int i=; i<n; i++) {
        if(i<maxright)
            hw[i]=min(hw[(mid<<)-i],hw[mid]+mid-i);
        else
            hw[i]=;
        while(s[i+hw[i]]==s[i-hw[i]])
            ++hw[i];
        if(hw[i]+i>maxright) {
            maxright=hw[i]+i;
            mid=i;
        }
    }
}//主函数更新答案 

马拉车算法