【BZOJ3676】【UOJ103】【APIO2014】【回文树模板题】回文串

Description

http://uoj.ac/problem/103

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Solution

回文树模板题。
感觉和SAM一个样啊
具体看2017年wwt的论文吧233

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Code

/************************************************
 * Au: Hany01
 * Date: Jun 21st, 2018
 * Prob: [BZOJ3676][APIO2014] 回文串
 * Email: [email protected]
 * Institute: Yali High School
************************************************/

#include<bits/stdc++.h>

using namespace std;

typedef long long LL;
typedef pair<int, int> PII;
#define File(a) freopen(a".in", "r", stdin), freopen(a".out", "w", stdout)
#define rep(i, j) for (register int i = 0, i##_end_ = (j); i < i##_end_; ++ i)
#define For(i, j, k) for (register int i = (j), i##_end_ = (k); i <= i##_end_; ++ i)
#define Fordown(i, j, k) for (register int i = (j), i##_end_ = (k); i >= i##_end_; -- i)
#define Set(a, b) memset(a, b, sizeof(a))
#define Cpy(a, b) memcpy(a, b, sizeof(a))
#define x first
#define y second
#define pb(a) push_back(a)
#define mp(a, b) make_pair(a, b)
#define ALL(a) (a).begin(), (a).end()
#define SZ(a) ((int)(a).size())
#define INF (0x3f3f3f3f)
#define INF1 (2139062143)
#define debug(...) fprintf(stderr, __VA_ARGS__)
#define y1 wozenmezhemecaia

template <typename T> inline bool chkmax(T &a, T b) { return a < b ? a = b, 1 : 0; }
template <typename T> inline bool chkmin(T &a, T b) { return b < a ? a = b, 1 : 0; }

inline int read()
{
    register int _, __; register char c_;
    for (_ = 0, __ = 1, c_ = getchar(); c_ < '0' || c_ > '9'; c_ = getchar()) if (c_ == '-') __ = -1;
    for ( ; c_ >= '0' && c_ <= '9'; c_ = getchar()) _ = (_ << 1) + (_ << 3) + (c_ ^ 48);
    return _ * __;
}

const int maxn = 300005;

char s[maxn];

struct PalindromicTree
{
    int ch[maxn][26], fa[maxn], len[maxn], sz[maxn], tot, las, n;

    inline void extend(int i)
    {
        register int p = las, c = s[i] - 97;
        while (s[i - len[p] - 1] != s[i]) p = fa[p];
        if (!ch[p][c]) {
            register int np = ++ tot, k = fa[p];
            len[np] = len[p] + 2;
            while (s[i - len[k] - 1] != s[i]) k = fa[k];
            fa[np] = ch[k][c], ch[p][c] = np;
        }
        ++ sz[las = ch[p][c]];
    }

    inline void init(char *s) {
        fa[0] = fa[1] = 1, len[tot = 1] = -1, n = strlen(s + 1);
        For(i, 1, n) extend(i);
    }

    inline void calc() {
        LL Ans = 0;
        Fordown(i, tot, 2) chkmax(Ans, (LL)len[i] * sz[i]), sz[fa[i]] += sz[i];
        printf("%lld\n", Ans);
    }

}PT;

int main()
{
#ifdef hany01
    File("bzoj3676");
#endif

    scanf("%s", s + 1), PT.init(s), PT.calc();

    return 0;
}
//闲坐悲君亦自悲，百年多是几多时。
//    -- 元稹《遣悲怀三首·其三》