算法总结:Manacher

先贴上大佬的Manacher讲解，用的Python，讲的很清楚:https://segmentfault.com/a/1190000003914228

然后讲一下自己对一些关键部分的理解（基于我的c++ code）和大佬的讲解:

 

第十九行代码:如果与i对应的已经计算出的j很小的化,那么这时候i的RL[i] = RL[j] = RL[2*pos - 1]

其他的大佬已经讲的很清楚了，很好理解，贴下自己的c++代码:

#include <iostream>
#include <cstring>
#include <cstdio>
#include <algorithm>
#include <string>
#define MAXN 1000001
using namespace std;

string s = "sator arepo tenet opera rotas";

int Manacher(string res)
{
    int i, pos = 0, MaxRight = 0, MaxLen = 0;
    int Len = res.size();
    int RL[Len];
    memset(RL, 0, sizeof(RL));
    for (i = 0; i < Len; ++i)
    {
        if (i < MaxRight)
            RL[i] = min(RL[2*pos-i], MaxRight - i);
        else
            RL[i] = 1;

        while (i + RL[i] < Len && i - RL[i] >= 0 && res[i - RL[i]] == res[i + RL[i]])
            RL[i]++;
        if (i + RL[i] - 1 > MaxRight)
        {
            MaxRight = i + RL[i] - 1;
            pos = i;
        }
        MaxLen = max(MaxLen, RL[i]);
    }

    return MaxLen - 1;
}

int main()
{
    string res;
    res += '#';
    for (unsigned int i = 0; i < s.size(); ++i)
    {
        res += s[i];
        res += '#';
    }

    cout << Manacher(res) << endl;

    return 0;
}