• [CTSC2012]熟悉的文章 [广义后缀自动机,二分+单调队列优化dp]


    题意:

    给定多个主串,每次将询问串拆分成多个连续子串,如果该子串在主串中出现,那么这段是合法的,要求一个最大的 (L) 使得合法的长度 (geq) 询问串长度的 (90\%)

    我们发现 (L) 是可以二分的,我们再考虑怎么 (check) 这个是否合法,对于一个 (L)

    我们设 (mx_i)(i) 节点结尾最长能匹配的长度。

    (F_i = max{F_{i-1},F_j+i-j} i - mx_i leq j leq i - L)

    我们发现 (i - mx_i)是非降的, (i-L) 是严格上升的,所以可以用单调队列 + (dp) 来判定可行性。

    // powered by c++11
    // by Isaunoya
    #include <bits/stdc++.h>
    #define rep(i, x, y) for (register int i = (x); i <= (y); ++i)
    #define Rep(i, x, y) for (register int i = (x); i >= (y); --i)
    using namespace std;
    using db = double;
    using ll = long long;
    using uint = unsigned int;
    #define Tp template
    using pii = pair<int, int>;
    #define fir first
    #define sec second
    Tp<class T> void cmax(T& x, const T& y) {
      if (x < y) x = y;
    }
    Tp<class T> void cmin(T& x, const T& y) {
      if (x > y) x = y;
    }
    #define all(v) v.begin(), v.end()
    #define sz(v) ((int)v.size())
    #define pb emplace_back
    Tp<class T> void sort(vector<T>& v) { sort(all(v)); }
    Tp<class T> void reverse(vector<T>& v) { reverse(all(v)); }
    Tp<class T> void unique(vector<T>& v) { sort(all(v)), v.erase(unique(all(v)), v.end()); }
    const int SZ = 1 << 23 | 233;
    struct FILEIN {
      char qwq[SZ], *S = qwq, *T = qwq, ch;
    #ifdef __WIN64
    #define GETC getchar
    #else
      char GETC() { return (S == T) && (T = (S = qwq) + fread(qwq, 1, SZ, stdin), S == T) ? EOF : *S++; }
    #endif
      FILEIN& operator>>(char& c) {
        while (isspace(c = GETC()))
          ;
        return *this;
      }
      FILEIN& operator>>(string& s) {
        while (isspace(ch = GETC()))
          ;
        s = ch;
        while (!isspace(ch = GETC())) s += ch;
        return *this;
      }
      Tp<class T> void read(T& x) {
        bool sign = 0;
        while ((ch = GETC()) < 48) sign ^= (ch == 45);
        x = (ch ^ 48);
        while ((ch = GETC()) > 47) x = (x << 1) + (x << 3) + (ch ^ 48);
        x = sign ? -x : x;
      }
      FILEIN& operator>>(int& x) { return read(x), *this; }
      FILEIN& operator>>(ll& x) { return read(x), *this; }
    } in;
    struct FILEOUT {
      const static int LIMIT = 1 << 22;
      char quq[SZ], ST[233];
      int sz, O;
      ~FILEOUT() { flush(); }
      void flush() {
        fwrite(quq, 1, O, stdout);
        fflush(stdout);
        O = 0;
      }
      FILEOUT& operator<<(char c) { return quq[O++] = c, *this; }
      FILEOUT& operator<<(string str) {
        if (O > LIMIT) flush();
        for (char c : str) quq[O++] = c;
        return *this;
      }
      Tp<class T> void write(T x) {
        if (O > LIMIT) flush();
        if (x < 0) {
          quq[O++] = 45;
          x = -x;
        }
        do {
          ST[++sz] = x % 10 ^ 48;
          x /= 10;
        } while (x);
        while (sz) quq[O++] = ST[sz--];
      }
      FILEOUT& operator<<(int x) { return write(x), *this; }
      FILEOUT& operator<<(ll x) { return write(x), *this; }
    } out;
    
    const int maxn = 2e6 + 62;
    char s[maxn];
    
    struct SAM {
      int cnt, las, ch[maxn][26], len[maxn], fa[maxn];
    
      SAM() { cnt = las = 1; }
    
      void ins(int c) {
        int p = las, np = las = ++cnt;
        len[np] = len[p] + 1;
        for (; p && !ch[p][c]; p = fa[p]) ch[p][c] = np;
        if (!p) {
          fa[np] = 1;
        } else {
          int q = ch[p][c];
          if (len[q] == len[p] + 1) {
            fa[np] = q;
          } else {
            int nq = ++cnt;
            memcpy(ch[nq], ch[q], sizeof(ch[q]));
            fa[nq] = fa[q], fa[q] = fa[np] = nq, len[nq] = len[p] + 1;
            for (; p && ch[p][c] == q; p = fa[p]) ch[p][c] = nq;
          }
        }
      }
    
      int mx[maxn];
    
      void find() {
        int L = strlen(s + 1), p = 1, mxl = 0;
        for (int i = 1; i <= L; i++) {
          int c = s[i] & 1;
          for (; p && !ch[p][c];) p = fa[p], mxl = len[p];
          if (p)
            p = ch[p][c], ++mxl;
          else
            p = 1, mxl = 0;
          mx[i] = mxl;
        }
      }
    
      int f[maxn], q[maxn];
      bool chk(int mid) {
        int L = strlen(s + 1), h, t;
        h = t = 0, q[++h] = 0;
        for (int i = 1; i <= mid - 1; i++) f[i] = 0;
        for (int i = mid; i <= L; i++) {
          f[i] = f[i - 1];
          while (h <= t && f[q[t]] - q[t] < f[i - mid] - (i - mid)) --t;
          q[++t] = i - mid;
          while (h <= t && q[h] < i - mx[i]) ++h;
          if (h <= t) cmax(f[i], f[q[h]] + i - q[h]);
        }
        return f[L] * 10 >= L * 9;
      }
    } sam;
    
    signed main() {
      // code begin.
      int _, n;
      scanf("%d %d" , & _ , & n) ;
      while (n--) {
        scanf("%s", s + 1);
        sam.las = 1;
        int len = strlen(s + 1);
        for (int i = 1; i <= len; i++) {
          sam.ins(s[i] & 1);
        }
      }
      while (_--) {
        scanf("%s", s + 1), sam.find();
        int l = 1, r = strlen(s + 1), ans = 0;
        while (l <= r) {
          int mid = l + r >> 1;
          if (sam.chk(mid)) {
            l = mid + 1;
            ans = mid;
          } else {
            r = mid - 1;
          }
        }
        out << ans << '
    ';
      }
      return 0;
      // code end.
    }
    
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  • 原文地址:https://www.cnblogs.com/Isaunoya/p/12510271.html
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