Manacher模板（回文字符串）

#include <iostream>
#include <cstring>
#include <cmath>
#define maxn 1010
using namespace std;
char help[maxn];

void ManacherString(string str);
int MaxLcpsLength(string str);


int MaxLcpsLength(string str)
{
    
    

    int len = (int)str.length() * 2 + 1;
    ManacherString(str);
    if(len == 0)return 0;
    int Arr[len];//回文半径
    int C = -1;//中心
    int R = -1;//回文右边界，最大右有效区为r-1
    int Max = INT_MIN;//cout<<Max<<endl;
    for(int i = 0;i < len;i++)
    {
    
    
        Arr[i] = R > i?min(Arr[2*C-1],R-i): 1 ;
        while(i + Arr[i] < len&&i - Arr[i] > -1)
        {
    
    
            if(help[i + Arr[i]] == help[i - Arr[i]])
                Arr[i]++;
            else break;
        }
        if(i + Arr[i] > R)
        {
    
    
            R = i + Arr[i];
            C = i;
        }
    Max = max(Max,Arr[i]);
    }
    return Max - 1;
}

void ManacherString(string str)
{
    
    
    memset(help,0,sizeof(help));
    int len = (int)str.length() *2+1;
    int index = 0;
    for(int i = 0;i < len;i++)
    {
    
    
        help[i] = i%2 == 0?'#':str[index++];
    }
    for(int i = 0;i < len;i++)cout<<help[i]<<endl;
}


int main()
{
    
    
    cout << MaxLcpsLength("bbbaaacddcaaa")<< endl;
    return 0;
}