Submission #857123

#	Time	Username	Problem	Language	Result	Execution time	Memory
857123		hgglmao	Necklace (Subtask 4) (BOI19_necklace4)	C++17	15 / 15	220 ms	852 KiB

necklace

#include <bits/stdc++.h>
#define TASK "necklace"

using namespace std;

typedef long long ll;
typedef pair<int, int> ii;
typedef pair<int, ll> ill;
typedef pair<ll, int> lli;
typedef pair<ll, ll> pll;

const int MAX = 6001;
const int MOD = 1e9 + 7;

string a, b;
int na, nb;
int rs, ra, rb;
int k1[MAX], k2[MAX];

void KYS(string s, int *kys)
{
        kys[0] = 0;
        for (int i = 1; i < s.size(); ++i)
        {
                int j = kys[i - 1];
                while (j > 0 && s[i] != s[j])
                        j = kys[j - 1];
                if (s[i] == s[j])
                        kys[i] = j + 1;
                else
                        kys[i] = 0;
        }
}

void SOLVE(bool revb)
{
        for (int i = 0; i < na; ++i)
        {
                string al = a.substr(0, i), ar = a.substr(i, na - i);
                string bl = b, br = b;
                reverse(al.begin(), al.end());
                reverse(br.begin(), br.end());

                KYS(al + "!" + bl, k1);
                KYS(ar + "!" + br, k2);

                for (int j = 1; j <= nb; ++j)
                        if (rs < k1[i + j] + k2[na + nb - i - j])
                        {
                                rs = k1[i + j] + k2[na + nb - i - j];
                                ra = i - k1[i + j];
                                if (revb)
                                        rb = nb - j - k2[na + nb - i - j];
                                else
                                        rb = j - k1[i + j];
                        }
        }
}

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

        if (fopen(TASK ".inp", "r"))
        {
                freopen(TASK ".inp", "r", stdin);
                freopen(TASK ".out", "w", stdout);
        }

        cin >> a >> b;
        na = a.size(), nb = b.size();

        SOLVE(0);
        reverse(b.begin(), b.end());
        SOLVE(1);

        cout << rs << '\n'
             << ra << ' ' << rb;
}

Compilation message (stderr)

necklace.cpp: In function 'void KYS(std::string, int*)':
necklace.cpp:23:27: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   23 |         for (int i = 1; i < s.size(); ++i)
      |                         ~~^~~~~~~~~~
necklace.cpp: In function 'int main()':
necklace.cpp:68:24: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   68 |                 freopen(TASK ".inp", "r", stdin);
      |                 ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~
necklace.cpp:69:24: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   69 |                 freopen(TASK ".out", "w", stdout);
      |                 ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 15 / 15