HDU3068 最长回文 Manacher's Algorithm 马拉车算法 模板

HDU3068

复习了一下这个算法，

注意数组大小要开两倍大。

    #include <algorithm>
    #include  <iterator>
    #include  <iostream>
    #include   <cstring>
    #include   <cstdlib>
    #include   <iomanip>
    #include    <bitset>
    #include    <cctype>
    #include    <cstdio>
    #include    <string>
    #include    <vector>
    #include     <cmath>
    #include     <queue>
    #include      <list>
    #include       <map>
    #include       <set>
    using namespace std;
    //#pragma GCC optimize(3)
    //#pragma comment(linker, "/STACK:102400000,102400000")  //c++
    #define lson (l , mid , rt << 1)
    #define rson (mid + 1 , r , rt << 1 | 1)
    #define debug(x) cerr << #x << " = " << x << "\n";
    #define pb push_back
    #define pq priority_queue



    typedef long long ll;
    typedef unsigned long long ull;

    typedef pair<ll ,ll > pll;
    typedef pair<int ,int > pii;
    typedef pair<int,pii> p3;

    //priority_queue<int> q;//这是一个大根堆q
    //priority_queue<int,vector<int>,greater<int> >q;//这是一个小根堆q
    #define fi first
    #define se second
    //#define endl '\n'

    #define OKC ios::sync_with_stdio(false);cin.tie(0)
    #define FT(A,B,C) for(int A=B;A <= C;++A)  //用来压行
    #define REP(i , j , k)  for(int i = j ; i <  k ; ++i)
    //priority_queue<int ,vector<int>, greater<int> >que;

    const ll mos = 0x7FFFFFFFLL;  //2147483647
    const ll nmos = 0x80000000LL;  //-2147483648
    const int inf = 0x3f3f3f3f;
    const ll inff = 0x3f3f3f3f3f3f3f3fLL; //18
    const int mod = 998244353;

    const double PI=acos(-1.0);

    // #define _DEBUG;         //*//
    #ifdef _DEBUG
    freopen("input", "r", stdin);
    // freopen("output.txt", "w", stdout);
    #endif
    /*-----------------------showtime----------------------*/
                int p[300009];
                char str[300009],t[300009];
                int Manacher(char *str,int len){
                    t[0] = '$';t[1] = '#';
                    int tot = 2;
                    for(int i=0; i<len; i++){
                        t[tot++]=str[i];
                        t[tot++]='#';
                    }

                    int mx = 0,id = 0,reslen = 0,resCenter = 0;
                    for(int i=0; i<tot; i++){
                        if(i<mx) p[i] = min(p[2*id - i] , mx - i);
                        else p[i] = 1;
                        while(t[i+p[i]] == t[i-p[i]])p[i] ++;
                        if(p[i]+i > mx){
                            mx = i + p[i];
                            id = i;
                        }
                        if(reslen < p[i]){reslen = p[i], resCenter = i;}

                    }
                    return reslen;
                }
    int main(){
                
                
                while(~scanf("%s", str)){
                    int len = strlen(str);
                    printf("%d\n",Manacher(str,len)-1);
                }
                return 0;
    }

HDU3068