Submission #1083629

#	Time	Username	Problem	Language	Result	Execution time	Memory
1083629		Joshua_Andersson	Necklace (Subtask 1-3) (BOI19_necklace1)	C++14	53 / 85	1401 ms	600 KiB

necklace

    #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 uint64_t ull;
    struct H {
        ull x; H(ull x = 0) : x(x) {}
        H operator+(H o) { return x + o.x + (x + o.x < x); }
        H operator-(H o) { return *this + ~o.x; }
        H operator*(H o) {
            auto m = (__uint128_t)x * o.x;
            return H((ull)m) + (ull)(m >> 64);
        }
        ull get() const { return x + !~x; }
        bool operator==(H o) const { return get() == o.get(); }
        bool operator!=(H o) const { return !(*this == o); }
        bool operator<(H o) const { return get() < o.get(); }
    };
    static const H C = (ll)1e11 + 3; // (order ~ 3e9; random also ok)
     
    struct HashInterval {
        vector<H> ha, pw;
        HashInterval(string& str) : ha(sz(str) + 1), pw(ha) {
            pw[0] = 1;
            repp(i, 0, sz(str))
                ha[i + 1] = ha[i] * C + str[i],
                pw[i + 1] = pw[i] * C;
        }
        H hashInterval(int a, int b) { // hash [a, b)
            b++;
            return ha[b] - ha[a] * pw[b - a];
        }
    };
     
     
     
    pair<int, p2> best(string a, string b, bool rev)
    {
        int ret = -1;
        p2 r = p2(-1, -1);
        HashInterval h1(a);
        HashInterval 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();
     
        while (chrono::duration_cast<chrono::milliseconds>(chrono::high_resolution_clock::now() - start).count() < 700)
        {
            int aa = da(rng);
            int ab = aa;
            int ba = db(rng);
            int bb = ba;
     
     
            int lo = -1;
            int hi = 4001;
            while (lo + 1 < hi)
            {
                int mid = (lo + hi) / 2;
                if (aa + mid >= sz(a) || ba + mid >= sz(b) || h1.hashInterval(aa, aa + mid) != h2.hashInterval(ba, ba + mid))
                {
                    hi = mid;
                }
                else lo = mid;
            }
            aa += hi;
            ba += hi;
     
            lo = -1;
            hi = 4001;
            while (lo + 1 < hi)
            {
                int mid = (lo + hi) / 2;
                if (ab - 1 - mid < 0 || bb - 1 - mid < 0 || h1.hashInterval(ab - 1 - mid, ab - 1) != h2.hashInterval(bb - 1 - mid, bb - 1))
                {
                    hi = mid;
                }
                else lo = mid;
            }
            ab -= hi;
            bb -= hi;
     
     
            //startb = sb;
            //startb = sb;
            //assert(starta != 1830);
            int starta = aa;
            int startb = bb;
     
            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.hashInterval(i, i + rlen - 1) == h2.hashInterval(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.hashInterval(i, i + llen - 1) == h2.hashInterval(j, j + llen - 1);
                if (good) lp = llen;
            }
     
            if (rp + lp > ret)
            {
                //assert(rp + lp != 84);
                r = { starta - rp,startb - lp };
                if (rev) r.second = sz(b) - r.second - rp - lp;
                //assert(r != p2(18, 54));
                ret = rp + lp;
                l = max(l, ret);
            }
        }
     
     
        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;
    }

• Subtask 1: 25 / 25
• Subtask 2: 20 / 20
• Subtask 3: 8 / 40