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  • [SP694][SP705]DISUBSTR

    (frac{n imes n+1}{2}) 个子串,减去重复的(height 的 和)

    “产生前缀” 的意思是 sa[i] 这个后缀有 n-sa[i]+1 个前缀

    #include <bits/stdc++.h>
    using namespace std;
    int k, n, rnk[50005], sa[50005], H[50005], c[50005], K;
    char s[50005];
    
    void Sort(int *x, int *y, int *rk) {
      static int C[50005];
      for (int i = 0; i <= k; ++i) C[i] = 0;
      for (int i = 1; i <= n; ++i) ++C[rk[i]];
      for (int i = 1; i <= k; ++i) C[i] += C[i - 1];
      for (int i = n; i; --i) y[C[rk[x[i]]]--] = x[i];
    }
    inline bool cmp(int *y, int a, int b, int m) {return y[a] == y[b] && y[a + m] == y[b + m];}
    void get_SA() {
      static int Y[50005];
      int *y = Y, *rk = rnk;
      for (int i = 1; i <= n; ++i) rk[i] = s[y[i] = i];
      k = 128;
      Sort(y, sa, rk);
      for (int m = 1, p = 0; p < n; k = p, m <<= 1) {
        for (p = 0; p < m; ++p) y[p + 1] = n - m + p + 1;
        for (int i = 1; i <= n; ++i) if (sa[i] > m) y[++p] = sa[i] - m;
        Sort(y, sa, rk), swap(y, rk);
        rk[sa[p = 1]] = 1;
        for (int i = 2; i <= n; ++i) rk[sa[i]] = cmp(y, sa[i], sa[i - 1], m) ? p : ++p;
      }
      for (int i = 1; i <= n; ++i) rnk[sa[i]] = i;
    }
    void get_H() {
      for (int i = 1, k = 0; i <= n; H[rnk[i++]] = k)
        for (k ? --k : 0; s[i + k] == s[sa[rnk[i] - 1] + k]; ++k);
    }
    
    int main() {
      cin >> K;
      while (~scanf("%s", s + 1)) {
        n = strlen(s + 1);
        get_SA();
        get_H();
        unsigned int ans = n * 1ll * (n + 1) / 2;
        for (int i = 2; i <= n; ++i) ans -= H[i];
        cout << ans << endl;
      }
      return 0;
    }
    
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  • 原文地址:https://www.cnblogs.com/storz/p/10607795.html
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