后缀数组模板

namespace SA
{
    int n, k, rk[MAXN], tmp[MAXN];

    bool compare_sa(int i, int j)
    {
        if (rk[i] != rk[j]) return rk[i] < rk[j];
        int ri = i + k <= n ? rk[i + k] : -1;      // 注意是 <= n
        int rj = j + k <= n ? rk[j + k] : -1;
        return ri < rj;
    }
    void construct_sa(string S, int* sa)
    {
        n = S.length();
        rep(i, n + 1) {       // 这里认为空串也是后缀
            sa[i] = i, rk[i] = i < n ? S[i] : -1;
        }
        for (k = 1; k <= n; k *= 2) {   // 已经计算好了长度小于等于k的所有后缀
            sort(sa, sa + n + 1, compare_sa);      // 注意下标是 0 ~ n
            tmp[sa[0]] = 0;
            rep1(i, n) tmp[sa[i]] = tmp[sa[i - 1]] + compare_sa(sa[i - 1], sa[i]);
            rep(i, n + 1) rk[i] = tmp[i];
        }
    }
    void construct_lcp(string S, int* sa, int* lcp)
    {
        n = S.length();
        rep(i, n + 1) rk[sa[i]] = i;

        int h = 0;
        rep(i, n) {
            int j = sa[rk[i] - 1];
            if (h > 0) h --;
            for (; j + h < n && i + h < n; ++ h) {
                if (S[j + h] != S[i + h]) break;
            }
            lcp[rk[i] - 1] = h;
        }
    }
}