oj.uz

답안 #678490

# 제출 시각 아이디 문제 언어 결과 실행 시간 메모리
678490 2023-01-06T04:45:46 Z cig32 Necklace (Subtask 1-3) (BOI19_necklace1) C++17
85 / 85
 377 ms 780 KB 
#include "bits/stdc++.h"
using namespace std;
#define int long long
const int MAXN = 3004;
const int MOD = 998244353;
mt19937_64 rng((int)std::chrono::steady_clock::now().time_since_epoch().count());
int rnd(int x, int y) {
  int u = uniform_int_distribution<int>(x, y)(rng); return u;
}
vector<int> prefix_function(string t) {
  int n = t.size();
  vector<int> lps(n);
  lps[0] = 0;
  for(int i=1; i<n; i++) {
    int j = lps[i-1];
    while(j > 0 && t[i] != t[j]) {
      j = lps[j-1];
    }
    if(t[i] == t[j]) lps[i] = j+1;
    else lps[i] = 0;
  }
  return lps;
}
int ans1, sst, tst;
int pows[6010];
int aa[6010], bb[6010];
const int factor = 2017;
int hasha(int l, int r) {
  int qq = aa[l-1] * pows[r - l + 1];
  qq %= MOD;
  int given = aa[r] - qq; 
  if(given < 0) given = (MOD - (abs(given) % MOD)) % MOD;
  else given %= MOD;
  return given;
}
int hashb(int l, int r) {
  int qq = bb[l-1] * pows[r - l + 1];
  qq %= MOD;
  int given = bb[r] - qq; 
  if(given < 0) given = (MOD - (abs(given) % MOD)) % MOD;
  else given %= MOD;
  return given;
}
pair<int, pair<int, int> > lcs(string a, string b) { // length, starting positions
  int n = a.size(), m = b.size();
  a = " " + a;
  b = " " + b;
  int dp[2][m+1];
  for(int i=0; i<2; i++) for(int j=0; j<=m; j++) dp[i][j] = 0;
  int ma = 0;
  for(int i=1; i<=n; i++) {
    for(int j=0; j<=m; j++) dp[i & 1][j] = 0;
    for(int j=1; j<=m; j++) {
      if(a[i] == b[j]) dp[i & 1][j] = dp[(i-1) & 1][j-1] + 1;
      else dp[i & 1][j] = 0;
      ma = max(ma, dp[i & 1][j]);
    }
  }
  aa[0] = bb[0] = 0;
  for(int i=1; i<=n; i++) aa[i] = (aa[i-1] * factor + a[i]) % MOD;
  for(int i=1; i<=m; i++) bb[i] = (bb[i-1] * factor + b[i]) % MOD;
  for(int i=1; i<=n-ma+1; i++) {
    for(int j=1; j<=m-ma+1; j++) {
      if(hasha(i, i+ma-1) == hashb(j, j+ma-1)) {
        return {ma, {i, j} };
      }
    }
  }
  assert(false);
}
void upd_ans(int new_len, int new_sst, int new_tst) {
  if(new_len > ans1) {
    ans1 = new_len;
    sst = new_sst;
    tst = new_tst;
  }
}
void out() {
  cout << ans1 << "\n";
  cout << sst - 1 << " " << tst - 1 << "\n";
}
string reversed(string x) {
  reverse(x.begin(), x.end());
  return x;
}
void solve(int tc) {
  pows[0] = 1;
  for(int i=1; i<6010; i++) pows[i] = (pows[i-1] * factor) % MOD;
  string s, t;
  cin >> s >> t;
  int n = s.size(), m = t.size();
  s = " " + s;
  t = " " + t;
  // Need to compute answer for both t and rev(t), both s and rev(s), for all suffixes of s and t
  // Can't be more duliu
 
  
  for(int i=2; i<=n; i++) {
    string u;
    u += s.substr(i, n - i + 1);
    u += "?";
    u += t.substr(1, m); // ~ 6000
    vector<int> lpsu = prefix_function(u);
    string v;
    v += reversed(s.substr(1, i-1));
    v += "?";
    v += reversed(t.substr(1, m));
    vector<int> lpsv = prefix_function(v);
    
    for(int j=1; j<m; j++) { // take [1, j]
      // j = 1: n - i + 2
      // j = x: n - i + x + 1 (0 based)
      int suf = lpsu[n-i+j+1];
      int pre = lpsv[i+m-j-1];
      // answer = pre + suf
      int inds = i - pre;
      int indt = j - suf + 1;
      upd_ans(pre + suf, inds, indt);
 
    }
  }
  reverse(t.begin() + 1, t.end());
 
  for(int i=2; i<=n; i++) {
    string u;
    u += s.substr(i, n - i + 1);
    u += "?";
    u += t.substr(1, m); // ~ 6000
    vector<int> lpsu = prefix_function(u);
    string v;
    v += reversed(s.substr(1, i-1));
    v += "?";
    v += reversed(t.substr(1, m));
    vector<int> lpsv = prefix_function(v);
    /*
    cout << u << "\n";
    for(int x: lpsu) cout << x << " ";
    cout << "\n";
    cout << v << "\n";
    for(int x: lpsv) cout << x << " ";
    cout << "\n";
    */
    for(int j=1; j<m; j++) { // take [1, j]
      // j = 1: n - i + 2
      // j = x: n - i + x + 1 (0 based)
      int suf = lpsu[n-i+j+1];
      int pre = lpsv[i+m-j-1];
      // answer = pre + suf
      int inds = i - pre;
      int indt = j + pre;
      indt = m - indt + 1;
      upd_ans(pre + suf, inds, indt);
 
    }
  }
 
  reverse(t.begin() + 1, t.end());
  
  // Remove whitespace
  s = s.substr(1, n);
  t = t.substr(1, m);
  // Compute lcs of s and t
  pair<int, pair<int, int> > res = lcs(s, t);
  upd_ans(res.first, res.second.first, res.second.second);
  // Compute lcs of s and rev(t)
  reverse(t.begin(), t.end());
  res = lcs(s, t);
  upd_ans(res.first, res.second.first, (int) m - res.second.second - res.first + 2);
 
  reverse(t.begin(), t.end());
  out();
}
int32_t main() {
  ios::sync_with_stdio(0); cin.tie(0);
  int t = 1; //cin >> t;
  for(int i=1; i<=t; i++) solve(i);
}

Subtask #1
25.0 / 25.0

# 결과 실행 시간 메모리 Grader output
1 Correct 1 ms 340 KB Output is correct
2 Correct 1 ms 348 KB Output is correct
3 Correct 2 ms 376 KB Output is correct
4 Correct 1 ms 340 KB Output is correct
5 Correct 1 ms 340 KB Output is correct

Subtask #2
20.0 / 20.0

# 결과 실행 시간 메모리 Grader output
1 Correct 1 ms 340 KB Output is correct
2 Correct 1 ms 348 KB Output is correct
3 Correct 2 ms 376 KB Output is correct
4 Correct 1 ms 340 KB Output is correct
5 Correct 1 ms 340 KB Output is correct
6 Correct 6 ms 340 KB Output is correct
7 Correct 6 ms 440 KB Output is correct
8 Correct 7 ms 376 KB Output is correct
9 Correct 6 ms 340 KB Output is correct
10 Correct 6 ms 340 KB Output is correct
11 Correct 5 ms 448 KB Output is correct
12 Correct 7 ms 376 KB Output is correct

Subtask #3
40.0 / 40.0

# 결과 실행 시간 메모리 Grader output
1 Correct 1 ms 340 KB Output is correct
2 Correct 1 ms 348 KB Output is correct
3 Correct 2 ms 376 KB Output is correct
4 Correct 1 ms 340 KB Output is correct
5 Correct 1 ms 340 KB Output is correct
6 Correct 6 ms 340 KB Output is correct
7 Correct 6 ms 440 KB Output is correct
8 Correct 7 ms 376 KB Output is correct
9 Correct 6 ms 340 KB Output is correct
10 Correct 6 ms 340 KB Output is correct
11 Correct 5 ms 448 KB Output is correct
12 Correct 7 ms 376 KB Output is correct
13 Correct 271 ms 528 KB Output is correct
14 Correct 260 ms 592 KB Output is correct
15 Correct 346 ms 624 KB Output is correct
16 Correct 377 ms 632 KB Output is correct
17 Correct 278 ms 624 KB Output is correct
18 Correct 213 ms 780 KB Output is correct
19 Correct 260 ms 536 KB Output is correct
20 Correct 285 ms 628 KB Output is correct
21 Correct 291 ms 656 KB Output is correct