马拉车算法

截图来自董老师https://www.bilibili.com/video/BV173411V7Ai/?spm_id_from=333.999.0.0&vd_source=23dc8e19d485a6ac47f03f6520fb15c2

  P3805 【模板】manacher 算法

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#include<iostream> #include<cstring> #include<cmath> #include<algorithm> #include<stack> #include<cstdio> #include<queue> #include<map> #include<vector> #include<set> using namespace std; const int maxn=3e7+10; const int INF=0x3fffffff; typedef long long LL;   char a[maxn],s[maxn]; int d[maxn]; void get_d(char *s,int n){     d[1]=1;     for(int i=2,l,r=1;i<=n;i++){         if(i<=r) d[i]=min(d[r-i+l],r-i+1);         while(s[i-d[i]]==s[i+d[i]]) d[i]++;         if(i+d[i]-1>r) {             l=i-d[i]+1;             r=i+d[i]-1;         }     } }   int main(){     scanf("%s",a+1);     int n=strlen(a+1);     int k=0;     s[0]='$';     s[++k]='#';     for(int i=1;i<=n;i++){         s[++k]=a[i];s[++k]='#';     }     n=k;     get_d(s,n);     int ans=0;     for(int i=1;i<=n;i++) ans=max(ans,d[i]);     printf("%d",ans-1); return 0; }