POJ 1743 Musical Theme

Description

A musical melody is represented as a sequence of N (1<=N<=20000)notes that are integers in the range 1..88, each representing a key on the piano. It is unfortunate but true that this representation of melodies ignores the notion of musical timing; but, this programming task is about notes and not timings. 
Many composers structure their music around a repeating &qout;theme&qout;, which, being a subsequence of an entire melody, is a sequence of integers in our representation. A subsequence of a melody is a theme if it: 

• is at least five notes long 
• appears (potentially transposed -- see below) again somewhere else in the piece of music 
• is disjoint from (i.e., non-overlapping with) at least one of its other appearance(s)

Transposed means that a constant positive or negative value is added to every note value in the theme subsequence. 

Given a melody, compute the length (number of notes) of the longest theme. 

One second time limit for this problem's solutions! 

Input

The input contains several test cases. The first line of each test case contains the integer N. The following n integers represent the sequence of notes. 
The last test case is followed by one zero. 

Output

For each test case, the output file should contain a single line with a single integer that represents the length of the longest theme. If there are no themes, output 0.

Sample Input

30 25 27 30 34 39 45 52 60 69 79 69 60 52 45 39 34 30 26 22 18 82 78 74 70 66 67 64 60 65 80 0

Sample Output

5

后缀数组+二分

#include<iostream>
#include<cmath>
#include<map>
#include<vector>
#include<queue>
#include<cstdio>
#include<cstring>
#include<algorithm>
using namespace std;
const int Min = 0;
const int Max = 0x7FFFFFFF;
const int maxn = 20005;
const int bit = 256;
class suffix
{
private:
  int s[maxn];
  int r[maxn], w[maxn], ss[maxn], h[maxn];
  int sa[maxn], rk[maxn + maxn], size;
  int size1;
public:
  bool get(){
    if (scanf("%d", &size) != 1 || size == 0)return false;
    for (int i = 1; i <= size; i++) scanf("%d", &s[i]);
    for (int i = 1; i <= size; i++) s[i] = s[i + 1] - s[i] + 88;
    s[size] = 0;
    return true;
  }
  void pre()
  {
    memset(rk, 0, sizeof(rk));
    for (int i = 1; i <= bit; i++) w[i] = 0;
    for (int i = 1; i <= size; i++) w[(int)s[i]]++;
    for (int i = 1; i <= bit; i++) w[i] += w[i - 1];
    for (int i = size; i; i--) sa[w[(int)s[i]]--] = i;
    for (int i = 1, j = 1; i <= size; i++)
      rk[sa[i]] = (s[sa[i]] == s[sa[i + 1]] ? j : j++);
    for (int j = 1; j < size; j += j)
    {
      for (int i = 1; i <= size; i++) w[i] = 0;
      for (int i = 1; i <= size; i++) w[rk[i + j]]++;
      for (int i = 1; i <= size; i++) w[i] += w[i - 1];
      for (int i = size; i; i--) ss[w[rk[i + j]]--] = i;

      for (int i = 1; i <= size; i++) w[i] = 0;
      for (int i = 1; i <= size; i++) w[rk[ss[i]]]++;
      for (int i = 1; i <= size; i++) w[i] += w[i - 1];
      for (int i = size; i; i--) sa[w[rk[ss[i]]]--] = ss[i];

      for (int i = 1, k = 1; i <= size; i++)
        r[sa[i]] = (rk[sa[i]] == rk[sa[i + 1]] && rk[sa[i] + j] == rk[sa[i + 1] + j]) ? k : k++;
      for (int i = 1; i <= size; i++) rk[i] = r[i];
    }
    for (int i = 1, k = 0, j; i <= size; h[rk[i++]] = k)
    for (k ? k-- : 0, j = sa[rk[i] - 1]; s[i + k] == s[j + k]; k++);
  }
  void work()
  {
    int mid, l = 0, r = size >> 1;
    for (mid = (l + r) >> 1; l < r;)
    {
      int minx = Max, maxx = Min, f = 0;
      for (int i = 2; i <= size; i++)
      {
        if (h[i] < mid)
        {
          minx = Max;
          maxx = Min;
        }
        else
        {
          minx = min(minx, min(sa[i], sa[i - 1]));
          maxx = max(maxx, max(sa[i], sa[i - 1]));
          if (maxx - minx >= mid)
          {
            f = 1;
            break;
          }
        }
      }
      if (f) l = mid; else r = mid - 1;
      mid = (l + r) >> 1;
      if (l + 1 == r) mid++;
    }
    if (mid >= 4) printf("%d\n", mid + 1);
    else puts("0");
  }
}f;

int main()
{
  while (f.get())
  {
    f.pre();
    f.work();
  }
  return 0;
}

最近重新回顾了一遍写了新的板子。

#include<set>
#include<map>
#include<ctime>
#include<cmath>
#include<stack>
#include<queue>
#include<bitset>
#include<cstdio>
#include<string>
#include<cstring>
#include<iostream>
#include<algorithm>
#include<functional>
#define rep(i,j,k) for (int i = j; i <= k; i++)
#define per(i,j,k) for (int i = j; i >= k; i--)
#define lson x << 1, l, mid
#define rson x << 1 | 1, mid + 1, r
using namespace std;
typedef long long LL;
const int low(int x) { return x&-x; }
const double eps = 1e-8;
const int INF = 0x7FFFFFFF;
const int mod = 1e9 + 7;
const int N = 2e4 + 10;
int T, n, s[N];

struct Sa
{
  //char s[N];
  int rk[2][N], sa[N], h[N], w[N], now;
  int rmq[N][20], lg[N];

  void GetS()
  {
    //scanf("%s", s + 1);
    getchar();
    //gets(s + 1);
    //gets_s(s + 1, N);
  }

  void getsa(int z, int &m)
  {
    int x = now, y = now ^= 1;
    rep(i, 1, z) rk[y][i] = n - i + 1;
    for (int i = 1, j = z; i <= n; i++)
      if (sa[i] > z) rk[y][++j] = sa[i] - z;

    rep(i, 1, m) w[i] = 0;
    rep(i, 1, n) w[rk[x][rk[y][i]]]++;
    rep(i, 1, m) w[i] += w[i - 1];
    per(i, n, 1) sa[w[rk[x][rk[y][i]]]--] = rk[y][i];
    for (int i = m = 1; i <= n; i++)
    {
      int *a = rk[x] + sa[i], *b = rk[x] + sa[i - 1];
      rk[y][sa[i]] = *a == *b&&*(a + z) == *(b + z) ? m - 1 : m++;
    }
  }

  void getsa(int m)
  {
    now = 0; //n = strlen(s + 1);
    rep(i, 1, m) w[i] = 0;
    rep(i, 1, n) w[s[i]]++;
    rep(i, 1, m) rk[1][i] = rk[1][i - 1] + (bool)w[i];
    rep(i, 1, m) w[i] += w[i - 1];
    rep(i, 1, n) rk[0][i] = rk[1][s[i]];
    rep(i, 1, n) sa[w[s[i]]--] = i;
    for (int x = 1, y = rk[1][m]; x <= n && y <= n; x <<= 1) getsa(x, y);
    for (int i = 1, j = 0; i <= n; h[rk[now][i++]] = j ? j-- : 0)
      while (s[sa[rk[now][i] - 1] + j] == s[i + j]) ++j;
  }

  void getrmq()
  {
    lg[1] = 0;
    rep(i, 2, n) rmq[i][0] = h[i], lg[i] = lg[i >> 1] + 1;
    for (int i = 1; (1 << i) <= n; i++)
    {
      rep(j, 2, n)
      {
        if (j + (1 << i) > n + 1) break;
        rmq[j][i] = min(rmq[j][i - 1], rmq[j + (1 << i - 1)][i - 1]);
      }
    }
  }

  int lcp(int x, int y)
  {
    int l = min(rk[now][x], rk[now][y]) + 1, r = max(rk[now][x], rk[now][y]);
    return min(rmq[l][lg[r - l + 1]], rmq[r - (1 << lg[r - l + 1]) + 1][lg[r - l + 1]]);
  }
  bool check(int x)
  {
    int l = sa[1], r = sa[1];
    for (int i = 1; i < n; i++)
    {
      if (h[i + 1] >= x) l = min(l, sa[i + 1]), r = max(r, sa[i + 1]);
      else
      {
        if (r - l >= x) return true;
        l = r = sa[i + 1];
      }
    }
    return r - l >= x;
  }
  void work()
  {
    int l = 4, r = n / 2;
    while (l <= r)
    {
      if (check(l + r >> 1)) l = (l + r >> 1) + 1;
      else r = (l + r >> 1) - 1;
    }
    printf("%d\n", l > 4 ? l : 0);
  }
}sa;

int main()
{
  while (scanf("%d", &n), n)
  {
    rep(i, 1, n) scanf("%d", &s[i]);
    --n;
    rep(i, 1, n) s[i] = s[i + 1] - s[i] + 88;
    sa.getsa(200);
    sa.work();
  }
  return 0;
}