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Submission #1083319

# Submission time Handle Problem Language Result Execution time Memory
1083319 2024-09-02T23:17:45 Z Joshua_Andersson Necklace (Subtask 1-3) (BOI19_necklace1) C++14
53 / 85
 1200 ms 856 KB 
#include <bits/stdc++.h>
using namespace std;

typedef long long ll;
#define int ll
const int inf = int(1e18);

typedef vector<int> vi;
typedef vector<vi> vvi;
typedef pair<int, int> p2;

#define rep(i, high) for (int i = 0; i < high; i++)
#define repp(i, low, high) for (int i = low; i < high; i++)
#define repe(i, container) for (auto& i : container)
#define sz(container) ((int)container.size())
#define all(x) begin(x),end(x)

inline void fast() { ios::sync_with_stdio(0); cin.tie(0); cout.tie(0); }

#if _LOCAL
#define assert(x) if (!(x)) __debugbreak()
#endif

typedef unsigned long long ull;

struct RollingHash
{
    vector<ull> suf, b;
    int mod;
    RollingHash(string& s, ull base = 131, ull mod = 1e9 + 7) : mod(mod), suf(s.size() + 1), b(s.size() + 1)
    {
        b[0] = 1;
        b[1] = base;

        for (int i = sz(s) - 1; i >= 0; i--)
        {
            suf[i] = (suf[i + 1] * base + s[i]) % mod;
        }

        repp(i, 2, s.size() + 1)
        {
            b[i] = b[i - 1] * b[1] % mod;
        }
    }

    ull gethash(int l, int r) // hash s[l, r]
    {
        ull rv = (suf[r + 1] * b[r - l + 1]) % mod;
        return suf[l] + mod * (suf[l] < rv) - rv;
    }
};

struct DoubleHash
{
    RollingHash h1;
    RollingHash h2;
    DoubleHash(string& s, ull mod = 1e9 + 7) : h1(s, 157, mod), h2(s, 131, mod) {}
    ull gethash(int l, int r)
    {
        return (h1.gethash(l, r) << 32) + h2.gethash(l, r);
    }
};

pair<int,p2> best(string a, string b, bool rev)
{
    int ret = -1;
    p2 r = p2(-1, -1);
    DoubleHash h1(a);
    DoubleHash h2(b);
    mt19937 rng;
    uniform_int_distribution<int> da(0, sz(a) - 1);
    uniform_int_distribution<int> db(0, sz(b) - 1);
    int l = 10;
    auto start = chrono::high_resolution_clock::now();

    int rounds = 0;
    while (chrono::duration_cast<chrono::milliseconds>(chrono::high_resolution_clock::now() - start).count() < 600)
    {
        int aa = da(rng);
        int ab = aa;
        int ba = db(rng);
        int bb = ba;

        int lo = -1;
        int hi = 4000;
        while (lo + 1 < hi)
        {
            int mid = (lo + hi) / 2;
            if (aa + mid >= sz(a) || ba + mid >= sz(b) || h1.gethash(aa, aa+mid) != h2.gethash(ba, ba+mid))
            {
                hi = mid;
            }
            else lo = mid;
        }
        aa += hi;
        ba += hi;


        while (ab > 0 && bb > 0 && a[ab-1] == b[bb-1])
        {
            ab--;
            bb--;
        }
        
        int starta = aa;
        int startb = bb;
        if (rand()%2)
        {
            starta = ab;
            startb = ba;
        }
        //if (len+1 < l) continue;
        rounds++;


        int rp = 0;
        repp(rlen, 1, l * 2 + 1)
        {
            int i = starta - rlen;
            int j = startb;
            if (i < 0 || j + rlen - 1 >= sz(b)) break;
            bool good = h1.gethash(i, i + rlen - 1) == h2.gethash(j, j + rlen - 1);
            if (good) rp = rlen;
        }
        int lp = 0;
        repp(llen, 1, l * 2 + 1)
        {
            int i = starta;
            int j = startb - llen;
            if (j < 0 || i + llen - 1 >= sz(a)) break;
            bool good = h1.gethash(i, i + llen - 1) == h2.gethash(j, j + llen - 1);
            if (good) lp = llen;
        }

        if (rp + lp > ret)
        {
            r = { starta - rp,startb - lp };
            if (rev) r.second = sz(b) - r.second - rp - lp;
            ret = rp + lp;
            l = max(l, ret);
        }
    }
    cerr << "rounds: " << rounds << "\n";

    return { ret, r };
}

signed main()
{
    fast();

    string a, b;
    cin >> a >> b;
    pair<int, p2> ans = { -1000,p2(0,0) };
    ans = max(ans, best(a, b, 0));
    reverse(all(b));
    ans = max(ans, best(a, b, 1));
    cout << ans.first << "\n" << ans.second.first << " " << ans.second.second;

    return 0;
}

Compilation message

necklace.cpp: In constructor 'RollingHash::RollingHash(std::string&, ull, ull)':
necklace.cpp:29:9: warning: 'RollingHash::mod' will be initialized after [-Wreorder]
   29 |     int mod;
      |         ^~~
necklace.cpp:28:17: warning:   'std::vector<long long unsigned int> RollingHash::suf' [-Wreorder]
   28 |     vector<ull> suf, b;
      |                 ^~~
necklace.cpp:30:5: warning:   when initialized here [-Wreorder]
   30 |     RollingHash(string& s, ull base = 131, ull mod = 1e9 + 7) : mod(mod), suf(s.size() + 1), b(s.size() + 1)
      |     ^~~~~~~~~~~
necklace.cpp:13:48: warning: comparison of integer expressions of different signedness: 'll' {aka 'long long int'} and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   13 | #define repp(i, low, high) for (int i = low; i < high; i++)
......
   40 |         repp(i, 2, s.size() + 1)
      |              ~~~~~~~~~~~~~~~~~~                 
necklace.cpp:40:9: note: in expansion of macro 'repp'
   40 |         repp(i, 2, s.size() + 1)
      |         ^~~~

Subtask #1
25.0 / 25.0

# Verdict Execution time Memory Grader output
1 Correct 1199 ms 436 KB Output is correct
2 Correct 1199 ms 344 KB Output is correct
3 Correct 1185 ms 440 KB Output is correct
4 Correct 1187 ms 452 KB Output is correct
5 Correct 1195 ms 344 KB Output is correct

Subtask #2
20.0 / 20.0

# Verdict Execution time Memory Grader output
1 Correct 1199 ms 436 KB Output is correct
2 Correct 1199 ms 344 KB Output is correct
3 Correct 1185 ms 440 KB Output is correct
4 Correct 1187 ms 452 KB Output is correct
5 Correct 1195 ms 344 KB Output is correct
6 Correct 1187 ms 460 KB Output is correct
7 Correct 1193 ms 348 KB Output is correct
8 Correct 1190 ms 712 KB Output is correct
9 Correct 1200 ms 348 KB Output is correct
10 Correct 1199 ms 348 KB Output is correct
11 Correct 1199 ms 856 KB Output is correct
12 Correct 1193 ms 460 KB Output is correct

Subtask #3
8.0 / 40.0

# Verdict Execution time Memory Grader output
1 Correct 1199 ms 436 KB Output is correct
2 Correct 1199 ms 344 KB Output is correct
3 Correct 1185 ms 440 KB Output is correct
4 Correct 1187 ms 452 KB Output is correct
5 Correct 1195 ms 344 KB Output is correct
6 Correct 1187 ms 460 KB Output is correct
7 Correct 1193 ms 348 KB Output is correct
8 Correct 1190 ms 712 KB Output is correct
9 Correct 1200 ms 348 KB Output is correct
10 Correct 1199 ms 348 KB Output is correct
11 Correct 1199 ms 856 KB Output is correct
12 Correct 1193 ms 460 KB Output is correct
13 Correct 1188 ms 604 KB Output is correct
14 Correct 1195 ms 848 KB Output is correct
15 Correct 1190 ms 828 KB Output is correct
16 Correct 1198 ms 852 KB Output is correct
17 Correct 1194 ms 644 KB Output is correct
18 Correct 1197 ms 604 KB Output is correct
19 Correct 1199 ms 648 KB Output is correct
20 Correct 1197 ms 600 KB Output is correct
21 Partially correct 1199 ms 600 KB Output is partially correct