oj.uz

Submission #1005549

# Submission time Handle Problem Language Result Execution time Memory
1005549 2024-06-22T15:30:36 Z anango Necklace (Subtask 1-3) (BOI19_necklace1) C++17
45 / 85
 486 ms 500 KB 
#include <bits/stdc++.h>
#define int long long
#define rng rand
using namespace std;

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<1000000; 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<=2*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)) {
                continue;
            }
            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 145 ms 408 KB Output is correct
2 Correct 68 ms 344 KB Output is correct
3 Correct 317 ms 348 KB Output is correct
4 Correct 178 ms 348 KB Output is correct
5 Correct 33 ms 424 KB Output is correct

Subtask #2
20.0 / 20.0

# Verdict Execution time Memory Grader output
1 Correct 145 ms 408 KB Output is correct
2 Correct 68 ms 344 KB Output is correct
3 Correct 317 ms 348 KB Output is correct
4 Correct 178 ms 348 KB Output is correct
5 Correct 33 ms 424 KB Output is correct
6 Correct 132 ms 348 KB Output is correct
7 Correct 60 ms 344 KB Output is correct
8 Correct 369 ms 348 KB Output is correct
9 Correct 202 ms 344 KB Output is correct
10 Correct 7 ms 344 KB Output is correct
11 Correct 9 ms 448 KB Output is correct
12 Correct 365 ms 348 KB Output is correct

Subtask #3
0.0 / 40.0

# Verdict Execution time Memory Grader output
1 Correct 145 ms 408 KB Output is correct
2 Correct 68 ms 344 KB Output is correct
3 Correct 317 ms 348 KB Output is correct
4 Correct 178 ms 348 KB Output is correct
5 Correct 33 ms 424 KB Output is correct
6 Correct 132 ms 348 KB Output is correct
7 Correct 60 ms 344 KB Output is correct
8 Correct 369 ms 348 KB Output is correct
9 Correct 202 ms 344 KB Output is correct
10 Correct 7 ms 344 KB Output is correct
11 Correct 9 ms 448 KB Output is correct
12 Correct 365 ms 348 KB Output is correct
13 Correct 142 ms 348 KB Output is correct
14 Partially correct 75 ms 500 KB Output is partially correct
15 Partially correct 486 ms 348 KB Output is partially correct
16 Partially correct 231 ms 348 KB Output is partially correct
17 Incorrect 3 ms 344 KB Output isn't correct
18 Halted 0 ms 0 KB -