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Submission #1118475

# Submission time Handle Problem Language Result Execution time Memory
1118475 2024-11-25T14:19:05 Z VinhLuu Palindromes (APIO14_palindrome) C++17
100 / 100
 880 ms 48296 KB 
#include <bits/stdc++.h>
//#define int long long
#define ll long long
#define fi first
#define se second
#define pb push_back
#define all(lmao) lmao.begin(), lmao.end()

using namespace std;

typedef pair<ll, ll> pii;

const int N = 3e5 + 5;
const int M = 1e6 + 5;
const ll oo = 1e16;

int n, a[N];

int pos[N], sa[N], gap, tmp[N], lcp[N], LG[N], dp[22][N];
ll ans = 0;

bool cmp(int x,int y){
  if(pos[x] != pos[y]) return pos[x] < pos[y];
  x += gap;
  y += gap;
  return (x <= n && y <= n ? pos[x] < pos[y] : x > y);
}

void SA(){
  gap = 1;
  for(int i = 1; i <= n; i ++) pos[i] = a[i], sa[i] = i;
  while(true){
    sort(sa + 1, sa + n + 1, cmp);
    for(int i = 2; i <= n; i ++) tmp[i] = tmp[i - 1] + cmp(sa[i - 1], sa[i]);
    for(int i = 1; i <= n; i ++) pos[sa[i]] = tmp[i] + 1;
    if(tmp[n] == n - 1) break;
    gap = gap * 2;
  }


  for(int i = 1, k = 0; i <= n; i ++){
    if(pos[i] == n) continue;
    for(int j = sa[pos[i] + 1]; a[i + k] == a[j + k]; ) k ++;
    lcp[pos[i]] = k;
    if(k) k--;
  }

  for(int i = 1; i <= n; i ++) LG[i] = (i == 1 ? 0 : LG[i / 2] + 1);
  for(int i = n; i >= 1; i --){
    dp[0][i] = lcp[i];
    for(int j = 1; j <= 20 && i + (1 << j) - 1 <= n; j ++){
      dp[j][i] = min(dp[j - 1][i], dp[j - 1][i + (1 << (j - 1))]);
    }
  }
}

int kq[2][N];

namespace Hash{
  #define int long long
  mt19937 rd(2615367263);
  int ra(int l,int r){
    return l + rd() % (r - l + 1);
  }

  const int MOD[2] = {ra(1e9, 2e9), (int)1e9 + 7};
  const int base = 137;

  int pw[2][N], h[2][N], g[2][N];

  int get(int l,int r){
    int A = (h[0][r] + MOD[0] - h[0][l - 1] * pw[0][r - l + 1] % MOD[0]) % MOD[0];
    int B = (h[1][r] + MOD[1] - h[1][l - 1] * pw[1][r - l + 1] % MOD[1]) % MOD[1];
    return A * MOD[1] + B;
  }

  int rev(int l,int r){
    int A = (g[0][l] + MOD[0] - g[0][r + 1] * pw[0][r - l + 1] % MOD[0]) % MOD[0];
    int B = (g[1][l] + MOD[1] - g[1][r + 1] * pw[1][r - l + 1] % MOD[1]) % MOD[1];
    return A * MOD[1] + B;
  }

  void solve(){
    pw[0][0] = pw[1][0] = 1;
    for(int i = 1; i <= n; i ++) for(int j = 0; j <= 1; j ++){
      pw[j][i] = pw[j][i - 1] * base % MOD[j];
      h[j][i] = (h[j][i - 1] * base % MOD[j] + a[i]) % MOD[j];
    }

    for(int i = n; i >= 1; i --) for(int j = 0; j <= 1; j ++) {
      g[j][i] = (g[j][i + 1] * base % MOD[j] + a[i]) % MOD[j];
    }

    for(int i = 1; i <= n; i ++){
      int l = 1, r = min(n - i, i);
      while(l <= r) {
        int mid = (l + r) / 2;
        if(get(i - mid + 1, i) == rev(i + 1, i + mid)){
          kq[0][i] = mid;
          l = mid + 1;
        }else r = mid - 1;
      }

      l = 1, r = min(n - i + 1, i);
      while(l <= r) {
        int mid = (l + r) / 2;
//        if(i == 4) {
//          cerr << i - mid + 1 << " " << i << " " << get(i - mid + 1, i) << " h\n";
//          cerr << i << " " << i + mid - 1
//        }
        if(get(i - mid + 1, i) == rev(i, i + mid - 1)){
          kq[1][i] = mid;
          l = mid + 1;
        }else r = mid - 1;
      }
    }
  }
}

int query(int l,int r){
  int k = LG[r - l + 1];
  return min(dp[k][l], dp[k][r - (1 << k) + 1]);
}

int bs(int x, int len){
  int i = pos[x];
  int l = 1, r = i - 1, _left = i;
  while(l <= r){
    int mid = (l + r) / 2;
    if(query(mid, i - 1) >= len){
      _left = mid;
      r = mid - 1;
    }else l = mid + 1;
  }
  l = i, r = n - 1;
  int _right = i;
  while(l <= r) {
    int mid = (l + r) / 2;
    if(query(i, mid) >= len){
      _right = mid + 1;
      l = mid + 1;
    }else r = mid - 1;
  }
  return _right - _left + 1;
}


signed main(){
  ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);

  #define task "v"
  if(fopen(task ".inp","r")){
    freopen(task ".inp","r",stdin);
    freopen(task ".out","w",stdout);
  }

  string s; cin >> s;
  n = s.size(); s = " " + s;
  for(int i = 1; i <= n; i ++) a[i] = (int)(s[i] - 'a') + 1;

  SA();

  Hash :: solve();

  for(int i = 1; i <= n; i ++){
    if(kq[0][i]){
      int tmp = bs(i - kq[0][i] + 1, 2 * kq[0][i]);
      ans = max(ans, 1ll * tmp * 2 * kq[0][i]);
    }
    if(kq[1][i]){
      int tmp = bs(i - kq[1][i] + 1, 2 * kq[1][i] - 1);
      ans = max(ans, 1ll * tmp * (2 * kq[1][i] - 1));
    }
  }
  cout << ans;
}

Compilation message

palindrome.cpp: In function 'int main()':
palindrome.cpp:153:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  153 |     freopen(task ".inp","r",stdin);
      |     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~
palindrome.cpp:154:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  154 |     freopen(task ".out","w",stdout);
      |     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~

Subtask #1
8.0 / 8.0

# Verdict Execution time Memory Grader output
1 Correct 3 ms 16736 KB Output is correct
2 Correct 3 ms 14672 KB Output is correct
3 Correct 3 ms 16720 KB Output is correct
4 Correct 2 ms 12792 KB Output is correct
5 Correct 3 ms 14672 KB Output is correct
6 Correct 2 ms 14672 KB Output is correct
7 Correct 3 ms 14672 KB Output is correct
8 Correct 1 ms 2396 KB Output is correct
9 Correct 2 ms 492 KB Output is correct
10 Correct 1 ms 764 KB Output is correct
11 Correct 1 ms 592 KB Output is correct
12 Correct 1 ms 592 KB Output is correct
13 Correct 2 ms 444 KB Output is correct
14 Correct 1 ms 600 KB Output is correct
15 Correct 2 ms 592 KB Output is correct
16 Correct 1 ms 592 KB Output is correct
17 Correct 1 ms 604 KB Output is correct
18 Correct 2 ms 6492 KB Output is correct
19 Correct 1 ms 604 KB Output is correct
20 Correct 1 ms 604 KB Output is correct
21 Correct 2 ms 6492 KB Output is correct
22 Correct 2 ms 608 KB Output is correct
23 Correct 1 ms 604 KB Output is correct
24 Correct 1 ms 604 KB Output is correct
25 Correct 1 ms 604 KB Output is correct
26 Correct 1 ms 604 KB Output is correct
27 Correct 4 ms 20828 KB Output is correct
28 Correct 4 ms 20828 KB Output is correct
29 Correct 4 ms 20828 KB Output is correct
30 Correct 3 ms 20828 KB Output is correct
31 Correct 4 ms 20968 KB Output is correct
32 Correct 4 ms 20960 KB Output is correct

Subtask #2
15.0 / 15.0

# Verdict Execution time Memory Grader output
1 Correct 6 ms 25216 KB Output is correct
2 Correct 5 ms 25168 KB Output is correct
3 Correct 4 ms 25168 KB Output is correct
4 Correct 4 ms 25168 KB Output is correct
5 Correct 3 ms 6736 KB Output is correct
6 Correct 3 ms 2640 KB Output is correct
7 Correct 3 ms 2640 KB Output is correct
8 Correct 2 ms 596 KB Output is correct
9 Correct 2 ms 592 KB Output is correct
10 Correct 2 ms 592 KB Output is correct
11 Correct 2 ms 592 KB Output is correct
12 Correct 2 ms 592 KB Output is correct

Subtask #3
24.0 / 24.0

# Verdict Execution time Memory Grader output
1 Correct 12 ms 1732 KB Output is correct
2 Correct 13 ms 3932 KB Output is correct
3 Correct 15 ms 7864 KB Output is correct
4 Correct 14 ms 1880 KB Output is correct
5 Correct 16 ms 1852 KB Output is correct
6 Correct 15 ms 1872 KB Output is correct
7 Correct 11 ms 1872 KB Output is correct
8 Correct 11 ms 1880 KB Output is correct
9 Correct 10 ms 1872 KB Output is correct
10 Correct 20 ms 29532 KB Output is correct

Subtask #4
26.0 / 26.0

# Verdict Execution time Memory Grader output
1 Correct 164 ms 37712 KB Output is correct
2 Correct 152 ms 37704 KB Output is correct
3 Correct 157 ms 37932 KB Output is correct
4 Correct 177 ms 19252 KB Output is correct
5 Correct 247 ms 14420 KB Output is correct
6 Correct 182 ms 14404 KB Output is correct
7 Correct 193 ms 14668 KB Output is correct
8 Correct 138 ms 16452 KB Output is correct
9 Correct 204 ms 37700 KB Output is correct
10 Correct 221 ms 37936 KB Output is correct

Subtask #5
27.0 / 27.0

# Verdict Execution time Memory Grader output
1 Correct 670 ms 44024 KB Output is correct
2 Correct 614 ms 44020 KB Output is correct
3 Correct 642 ms 48296 KB Output is correct
4 Correct 596 ms 46004 KB Output is correct
5 Correct 858 ms 43560 KB Output is correct
6 Correct 606 ms 47944 KB Output is correct
7 Correct 734 ms 44284 KB Output is correct
8 Correct 487 ms 44712 KB Output is correct
9 Correct 494 ms 44744 KB Output is correct
10 Correct 880 ms 46324 KB Output is correct
11 Correct 613 ms 44020 KB Output is correct
12 Correct 622 ms 48296 KB Output is correct