DC3求后缀数组板子

#include<bits/stdc++.h>
#define LL long long
#define fi first
#define se second
#define mk make_pair
#define PLL pair<LL, LL>
#define PLI pair<LL, int>
#define PII pair<int, int>
#define SZ(x) ((int)x.size())
#define ull unsigned long long

using namespace std;

const int N = 2e6 + 7;
const int inf = 0x3f3f3f3f;
const LL INF = 0x3f3f3f3f3f3f3f3f;
const int mod = 1000000007;
const double eps = 1e-6;
const double PI = acos(-1);

#define F(x) ((x) / 3 + ((x) % 3 == 1 ? 0 : tb))
#define G(x) ((x) < tb ? (x) * 3 + 1 : ((x) - tb) * 3 + 2)

int r[3 * N], sa[3 * N];
int wa[3 * N], wb[3 * N], wv[3 * N], ss[3 * N];
int rnk[N], lcp[N];

int c0(int *r, int a, int b) {return r[a] == r[b] && r[a + 1] == r[b + 1] && r[a + 2] == r[b + 2]; }

int c12(int k, int *r, int a, int b) {
    if(k == 2) return r[a] < r[b] || r[a] == r[b] && c12(1, r, a + 1, b + 1);
    return r[a] < r[b] || r[a] == r[b] && wv[a + 1] < wv[b + 1];
}

void sort(int *r, int *a, int *b, int n, int m) {
    for(int i = 0; i < n; i++) wv[i] = r[a[i]];
    for(int i = 0; i < m; i++) ss[i] = 0;
    for(int i = 0; i < n; i++) ss[wv[i]]++;
    for(int i = 1; i < m; i++) ss[i] += ss[i - 1];
    for(int i = n - 1; i >= 0; i--) b[--ss[wv[i]]] = a[i];
}

void DC3(int *r, int *sa, int n, int m) {
    int i, j, p;
    int *san = sa + n, *rn = r + n;
    int ta = 0, tb = (n + 1) / 3, tbc = 0;

    r[n] = r[n + 1] = 0;
    for(i = 0; i < n; i++) if(i % 3 != 0) wa[tbc++] = i;

    sort(r + 2, wa, wb, tbc, m);
    sort(r + 1, wb, wa, tbc, m);
    sort(r, wa, wb, tbc, m);

    for(p = 1, rn[F(wb[0])] = 0, i = 1; i < tbc; i++)
        rn[F(wb[i])] = c0(r, wb[i - 1], wb[i]) ? p - 1 : p++;

    if(p < tbc) DC3(rn, san, tbc, p);
    else for(i = 0; i < tbc; i++) san[rn[i]] = i;

    for(i = 0; i < tbc; i++) if(san[i] < tb) wb[ta++] = san[i] * 3;
    if(n % 3 == 1) wb[ta++] = n - 1;

    sort(r, wb, wa, ta, m);

    for(i = 0; i < tbc; i++) wv[wb[i] = G(san[i])] = i;
    for(i = 0, j = 0, p = 0; i < ta && j < tbc; p++)
        sa[p] = c12(wb[j] % 3, r, wa[i], wb[j]) ? wa[i++] : wb[j++];

    for( ; i < ta; p++) sa[p] = wa[i++];
    for( ; j < tbc; p++) sa[p] = wb[j++];
}


void calc_LCP(int *r, int *sa, int n) {
    int k = 0;
    for(int i = 0; i < n; i++) rnk[sa[i]] = i;
    for(int i = 0; i < n - 1; lcp[rnk[i++]] = k) {
        if(k) k--;
        for(int j = sa[rnk[i] - 1]; r[i + k] == r[j + k]; k++);
    }
}

int n, m, tot;
char S[N], T[N];

int main() {
    scanf("%s%s", S, T);
    n = strlen(S); m = strlen(T);
    for(int i = 0; i < n; i++) r[tot++] = S[i];
    r[tot++] = '$';
    for(int i = 0; i < m; i++) r[tot++] = T[i];
    DC3(r, sa, tot + 1, 256);
    calc_LCP(r, sa, tot + 1);
    return 0;
}

/*
*/