Manacher algorithm O (n) to find the longest palindrome substring in a string hdu 3068 (template title)

Manacher (horse-drawn car) algorithm can find the longest palindrome substring in O (n)

The principle of the algorithm is the use of an ID and MX at the time of matching, and the nature of a palindrome string symmetry, so in the complexity of the calculation, the preceding constants do not seem very large

HDU 3068 manacher Algorithm template problem

#include <bits/stdc++.h>using namespacestd;Const intmaxn=3e5+7;CharS[MAXN],STR[MAXN];intLen1,len2,p[maxn],ans;voidinit () {str[0]='#'; str[1]='#';  for(intI=0; i<len1;i++) {Str[i*2+2]=S[i]; Str[i*2+3]='#'; } len2=len1*2+2; STR[LEN2]='*';}voidManacher () {intId=0, mx=0;  for(intI=1; i<len2;i++){        if(mx>i) P[i]=min (p[id*2-i],mx-i); Elsep[i]=1;  for(; Str[i+p[i]]==str[i-p[i]];p [i]++); if(p[i]+i>MX) {MX=p[i]+i; ID=i; }    }    return ;}intMain () { while(~SCANF ("%s", s)) {Len1=strlen (s);        Init ();        Manacher (); Ans=0;  for(intI=1; i<len2;i++) {ans=Max (ans,p[i]); } printf ("%d\n", ans-1); }    return 0;}/*Aaaaabab*/

Manacher algorithm O (n) to find the longest palindrome substring in a string hdu 3068 (template title)