Submission #648725

#	Time	Username	Problem	Language	Result	Execution time	Memory
648725		Lobo	Necklace (Subtask 1-3) (BOI19_necklace1)	C++17	0 / 85	34 ms	1492 KiB

necklace

#include<bits/stdc++.h>
using namespace std;
const long long inf = (long long) 1e18 + 10;
const int inf1 = (int) 1e9 + 10;
#define int long long
#define dbl long double
#define endl '\n'
#define sc second
#define fr first
#define mp make_pair
#define pb push_back
#define all(x) x.begin(), x.end()

const int maxn = 3030;

string a,b;
int n, m, mod, pw[maxn], lra[maxn][maxn], lrb[maxn][maxn];

void solve() {
    cin >> a >> b;
    n = a.size();
    m = b.size();

    mod = 1e9+7;
    pw[0] = 1;
    pw[1] = 1e4+9;
    for(int i = 2; i <= max(n,m); i++) {
        pw[i] = pw[i-1]*pw[1]%mod;
    }

    map<int,int> st;
    for(int i = 0; i < n; i++) {
        int cur = 0;
        for(int j = i; j < n; j++) {
            cur = (cur+a[j]*pw[j-i])%mod;
            lra[i][j] = cur;
            st[cur] = i;
        }
    }

    for(int i = 0; i < m; i++) {
        int cur = 0;
        for(int j = i; j < m; j++) {
            cur = (cur+b[j]*pw[j-i])%mod;
            lrb[i][j] = cur;
        }
    }

    int ans = 0;
    int ansa,ansb;
    for(int i = 0; i < m; i++) {
        for(int j = i; j < m; j++) {
            for(int k = j; k < m; k++) {
                //(j,k) (i,j-1)
                int val = lrb[j][k]+ lrb[i][j-1]*pw[k-j+1];
                val%= mod;
                if(st.count(val) && k-i+1 > ans) {
                    ans = k-i+1;
                    ansa = st[val];
                    ansb = i;
                }
            }
        }
    }

    reverse(all(b));
    for(int i = 0; i < m; i++) {
        int cur = 0;
        for(int j = i; j < m; j++) {
            cur = (cur+b[j]*pw[j-i])%mod;
            lrb[i][j] = cur;
        }
    }

    for(int i = 0; i < m; i++) {
        for(int j = i; j < m; j++) {
            for(int k = j; k < m; k++) {
                //(j,k) (i,j-1)
                int val = lrb[j][k]+ lrb[i][j-1]*pw[k-j+1];
                val%= mod;
                if(st.count(val) && k-i+1 > ans) {
                    ans = k-i+1;
                    ansa = st[val];
                    ansb = m-k-1;
                }
            }
        }
    }

    cout << ans << endl;
    cout << ansa << " " << ansb << endl;
}

int32_t main() {
    ios::sync_with_stdio(false); cin.tie(0);

    // freopen("in.in", "r", stdin);
    // freopen("out.out", "w", stdout);
    int tt = 1;
    // cin >> tt;
    while(tt--) {
        solve();
    }

}

• Subtask 1: 0 / 25
• Subtask 2: 0 / 20
• Subtask 3: 0 / 40