HDU 3068 最长回文

最长回文串模板题

Manacher 算法

#include<cstdio>
#include<cstring>
#include<algorithm>
#include<iostream>
#include<cstdlib>
#include<string>
#include<cmath>
#include<vector>
using namespace std;
const int maxn=1e5+7;
const double eps=1e-8;
const double pi=acos(-1);
#define ll long long
#define clc(a,b) memset(a,b,sizeof(a))

int Proc(char pszIn[],char pszOut[])
{
    int nLen=1;
    pszOut[0]='$';
    int i=0;
    while(pszIn[i]!='')
    {
        pszOut[nLen++]='#';
        pszOut[nLen++]=pszIn[i];
        i++;
    }
    pszOut[nLen++]='#';
    pszOut[nLen]=0;
    return nLen;
}
void Manacher(int *p,char *str,int len)
{
    int mx=0,id=0;
    for(int i=0; i<len; i++)
    {
        p[i]=mx>i?min(p[2*id-i],mx-i):1;
        while(str[i+p[i]]==str[i-p[i]])p[i]++;
        if(i+p[i]>mx)
        {
            mx=i+p[i];
            id=i;
        }
    }
}
const int MAXN=220010;
char strIn[MAXN];
char strOut[MAXN];
int p[MAXN];
int main()
{
    while(scanf("%s",strIn)!=EOF)
    {
        int nLen=Proc(strIn,strOut);
        Manacher(p,strOut,nLen);
        int ans=1;
        for(int i=0; i<nLen; i++)
            ans=max(ans,p[i]);
        printf("%d
",ans-1);
    }
    return 0;
}