oj.uz

Submission #1005559

# Submission time Handle Problem Language Result Execution time Memory
1005559 2024-06-22T15:37:07 Z anango Necklace (Subtask 1-3) (BOI19_necklace1) C++17
45 / 85
 1500 ms 524 KB 
#include <bits/stdc++.h>
#define int long long

using namespace std;
mt19937 rng;
int INF = 1LL<<60;
int p = 2071723;
int MOD = 1000000033;

string a;
string b;
int n,m;

vector<int> hashes;

void compute_hash(string s) {
    int n1 = s.size();
    hashes.clear();
    hashes=vector<int>(n1+1,0);
    int ha = 0;
    for (int i=0; i<n1; i++) {
        ha += s[i]-'a';
        ha *= p;
        ha %= MOD;
        hashes[i+1] = ha;
    }
    
}

int exp(int p, int n) {
    int ans=1;
    int r = p;
    for (int i=0; i<30; i++) {
        if (n&(1<<i)) {
            ans*=r;
            ans%=MOD;
        }
        r*=r;
        r%=MOD;
    }
    return ans;
}

int gethash(int l, int r) {
    int h1 = hashes[l];
    int h2 = hashes[r+1];
    h1 *= exp(p,r-l+1);
    h1%=MOD;
    int dif = h2-h1;
    dif%=MOD;
    dif+=MOD;
    dif%=MOD;
    return dif;
}

bool check(int a, int b, int length) {
    return gethash(a,a+length-1)==gethash(b,b+length-1);
}
bool verify(int i, int j, int length) {
    //checks if i...i+length-1 in a = j...j+length-1 in b
    return gethash(i,length-1)==gethash(n+j, length-1);
}

vector<pair<int,int>> solve() {
    compute_hash(a+b);
    int ans = 0;
    pair<int,int> xpos;
    pair<int,int> ypos;
    for (int trial=0; trial*ans<7000000; trial++) {
        int i,j;
        i=rng()%n;  
        j=rng()%m;
        if (a[i]!=b[j]) {
            continue;
        }
        int l,r;
        l=0;
        r=0;
        while (l+i>=0 && l+j>=0 && a[i+l]==b[j+l]) {
            //cout << "doing " << i <<" " << l <<" " << a[i+l] <<" " << b[j+l] << endl;
            l--;
        }
        l++;
        while (r+i<=n-1 && r+j<=m-1 && a[i+r]==b[j+r]) {
            r++;
        }
        r--;
        int length = r-l+1;
        int subans = length;
        if (subans>ans) {
            ans=subans;
            xpos={i+l,i+l+length};
            ypos={j+l,j+l+length};
        }
        for (int blubber=1; blubber<=length; blubber++) { //add it on both sides
            int la = i+r+1;
            int ra = i+r+blubber;
            int lb = j+l-blubber;
            int rb = j+l-1;
            if (!(0<=la && la<=n-1) || !(0<=lb && rb<=m-1)) {
                break;
            }
            if (gethash(la,ra)==gethash(n+lb,n+rb)) {
                int subans = blubber+length;
                if (subans>ans) {
                    //cout << a <<" " << b <<" " << ans <<" " << i <<" " << j <<" " << blubber <<" " << subans << endl;
                    //cout << la <<" " << ra <<" " << lb <<" " << rb << endl;
                    ans=subans;
                    xpos = {i+l,ra};
                    ypos = {lb,j+r};
                }
            }
        }

    }
    return {{ans,ans},xpos,ypos};

    
}

signed main() {
    //freopen("input.txt","r", stdin);
    //freopen("output.txt","w",stdout);
    cin >> a;
    cin >> b;
    n=a.size();
    m=b.size();
    vector<pair<int,int>> ans2;
    vector<int> ans(3);
    ans2=solve();
    ans[0] = ans2[0].first;
    ans[1] = ans2[1].first;
    ans[2] = ans2[2].first;
    reverse(b.begin(), b.end());
    ans2 = solve();
    if (ans2[0].first>ans[0]) {
        ans[0] = ans2[0].first;
        ans[1] = ans2[1].first;
        ans[2] = m-ans2[2].second-1;
    }
    reverse(a.begin(), a.end());
    ans2 = solve();
    if (ans2[0].first>ans[0]) {
        ans[0] = ans2[0].first;
        ans[1] = n-ans2[1].second-1;
        ans[2] = m-ans2[2].second-1;
    }
    reverse(b.begin(), b.end());
    ans2 = solve();
    if (ans2[0].first>ans[0]) {
        ans[0] = ans2[0].first;
        ans[1] = n-ans2[1].second-1;
        ans[2] = ans2[2].first;
    }
    cout << ans[0] << endl;
    cout << ans[1] <<" " << ans[2] << endl;


    //want to store for each x and j, the smallest t such that match[x][t]+t = j
    

}

Subtask #1
25.0 / 25.0

# Verdict Execution time Memory Grader output
1 Correct 786 ms 412 KB Output is correct
2 Correct 344 ms 344 KB Output is correct
3 Correct 1261 ms 416 KB Output is correct
4 Correct 623 ms 348 KB Output is correct
5 Correct 123 ms 416 KB Output is correct

Subtask #2
20.0 / 20.0

# Verdict Execution time Memory Grader output
1 Correct 786 ms 412 KB Output is correct
2 Correct 344 ms 344 KB Output is correct
3 Correct 1261 ms 416 KB Output is correct
4 Correct 623 ms 348 KB Output is correct
5 Correct 123 ms 416 KB Output is correct
6 Correct 721 ms 436 KB Output is correct
7 Correct 378 ms 348 KB Output is correct
8 Correct 1326 ms 420 KB Output is correct
9 Correct 675 ms 416 KB Output is correct
10 Correct 30 ms 348 KB Output is correct
11 Correct 43 ms 348 KB Output is correct
12 Correct 1262 ms 416 KB Output is correct

Subtask #3
0.0 / 40.0

# Verdict Execution time Memory Grader output
1 Correct 786 ms 412 KB Output is correct
2 Correct 344 ms 344 KB Output is correct
3 Correct 1261 ms 416 KB Output is correct
4 Correct 623 ms 348 KB Output is correct
5 Correct 123 ms 416 KB Output is correct
6 Correct 721 ms 436 KB Output is correct
7 Correct 378 ms 348 KB Output is correct
8 Correct 1326 ms 420 KB Output is correct
9 Correct 675 ms 416 KB Output is correct
10 Correct 30 ms 348 KB Output is correct
11 Correct 43 ms 348 KB Output is correct
12 Correct 1262 ms 416 KB Output is correct
13 Correct 778 ms 488 KB Output is correct
14 Partially correct 430 ms 524 KB Output is partially correct
15 Execution timed out 1504 ms 344 KB Time limit exceeded
16 Halted 0 ms 0 KB -