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Submission #46645

# Submission time Handle Problem Language Result Execution time Memory
46645 2018-04-22T13:22:42 Z ngkan146 Palindromes (APIO14_palindrome) C++11
47 / 100
 1000 ms 48300 KB 
#include <bits/stdc++.h>
#define ll long long
using namespace std;
const ll mod = (ll) 1e9+9;
const ll base = 29;
int lg2[300005];
// remember to run this
void prepLg2(int bound){
    for(int i=2;i<=bound;i++)
        lg2[i] = lg2[i>>1] + 1;
}
struct suffixArray{
    vector <int> sa, saRank, tmp;
    vector <vector <int> > lcp;
    int strLen, gap;

    bool saCmp(int x,int y){
        if (saRank[x] != saRank[y])
            return saRank[x] < saRank[y];
        return x+gap < strLen && y+gap < strLen ? saRank[x+gap] < saRank[y+gap] : x > y;
    }

    void build_lcp(string &s){
        int k = 0;
        for(int i = 0; i < strLen; i ++){
            if (saRank[i] != strLen - 1){
                for (int j = sa[saRank[i] + 1]; max(i+k, j+k) < strLen && s[i + k] == s[j + k];)  ++k;
                lcp[saRank[i]][0] = k;
                if (k) k--;
            }
        }
        for(int k = 1; k < 20; k ++){
            for(int i = 0; i < strLen; i ++)
                if (i + (1<<k) < strLen)
                    lcp[i][k] = min(lcp[i][k-1], lcp[i+(1<<(k-1))][k-1]);
                else break;
        }
    }

    int getLcp(int l,int r){
        if (l > r)  swap(l, r);
        if (l == r) return strLen - sa[l];
        int k = lg2[r - l];
        return min(lcp[l][k], lcp[r-(1<<k)][k]);
    }

    void build(string &s, int isIndexFromOne = 0){
        strLen = s.size();
        sa.assign(strLen + 5, 0);
        saRank.assign(strLen + 5, 0);
        tmp.assign(strLen + 5, 0);
        lcp.assign(strLen + 5, vector<int>(20));
        //for(int i = 0; i < strLen; i ++)
        //    lcp[i].assign(20, 0);

        for(int i = 0; i < strLen; i ++)
            sa[i] = i, saRank[i] = s[i];

        for(gap = 1;;gap *= 2){
            sort(sa.begin(), sa.begin() + strLen, [&](int a, int b) {return this->saCmp(a, b);});
            //sort(sa.begin(), sa.begin() + strLen, saCmp);
            for(int i = 0; i < strLen; i ++) tmp[i+1] = tmp[i] + saCmp(sa[i], sa[i+1]);
            for(int i = 0; i < strLen; i ++) saRank[sa[i]] = tmp[i];
            if (tmp[strLen-1] == strLen-1) break;
        }
        build_lcp(s);
    }
};
int n;
string s[2];
suffixArray suff;
ll hashCode[2][300000], pBase[300000];
void prepHash(){
    pBase[0] = 1;
    for(int i=1;i<300000;i++)
        pBase[i] = pBase[i-1] * base % mod;

    hashCode[0][0] = s[0][0] - 'a';
    hashCode[1][0] = s[1][0] - 'a';
    for(int i=1;i<n;i++)
        hashCode[0][i] = (hashCode[0][i-1] + pBase[i] * (s[0][i] - 'a')) % mod,
        hashCode[1][i] = (hashCode[1][i-1] + pBase[i] * (s[1][i] - 'a')) % mod;
}
bool checkPalindrome(int l1,int r1){
    int l2 = n-1-r1;
    int r2 = n-1-l1;

    ll val1 = (hashCode[0][r1] - (l1 == 0 ? 0 : hashCode[0][l1-1]) + mod) % mod;
    ll val2 = (hashCode[1][r2] - (l2 == 0 ? 0 : hashCode[1][l2-1]) + mod) % mod;
    val1 = val1 * pBase[max(0, r2 - r1)] % mod;
    val2 = val2 * pBase[max(0, r1 - r2)] % mod;
    return val1 == val2;
}

int main(){
    prepLg2(300000);
    iostream::sync_with_stdio(0);
    cin >> s[0];
    n = s[0].size();

    s[1] = s[0];
    reverse(s[1].begin(), s[1].end());

    suff.build(s[0]);
    prepHash();

    ll ans = 0;
    for(int i=0;i<n;i++){
        //cout << "pos " << suff.sa[i] << endl;
        for(int j = suff.sa[i] + (i ? suff.lcp[i-1][0] : 0); j < suff.strLen; j++){
            // check palindrome
            if (!checkPalindrome(suff.sa[i], j)) continue;

            int len = j - suff.sa[i] + 1;
            int far = i;

            for(int k=20;k>=0;k--){
                if (far + (1<<k) < n && suff.getLcp(i, far + (1<<k)) >= len)
                    far += (1<<k);
            }
            //cout << suff.sa[i] << ' ' << j << ' ' << far - i + 1 << endl;
            ans = max(ans, 1ll * len * (far - i + 1));
        }
    }
    cout<< ans;
}

Subtask #1
8.0 / 8.0

# Verdict Execution time Memory Grader output
1 Correct 6 ms 3836 KB Output is correct
2 Correct 6 ms 3940 KB Output is correct
3 Correct 6 ms 3980 KB Output is correct
4 Correct 6 ms 4052 KB Output is correct
5 Correct 6 ms 4052 KB Output is correct
6 Correct 6 ms 4052 KB Output is correct
7 Correct 6 ms 4052 KB Output is correct
8 Correct 6 ms 4052 KB Output is correct
9 Correct 6 ms 4052 KB Output is correct
10 Correct 7 ms 4052 KB Output is correct
11 Correct 7 ms 4052 KB Output is correct
12 Correct 7 ms 4176 KB Output is correct
13 Correct 6 ms 4228 KB Output is correct
14 Correct 6 ms 4228 KB Output is correct
15 Correct 6 ms 4228 KB Output is correct
16 Correct 6 ms 4228 KB Output is correct
17 Correct 7 ms 4228 KB Output is correct
18 Correct 6 ms 4228 KB Output is correct
19 Correct 6 ms 4228 KB Output is correct
20 Correct 6 ms 4228 KB Output is correct
21 Correct 6 ms 4228 KB Output is correct
22 Correct 7 ms 4228 KB Output is correct
23 Correct 6 ms 4228 KB Output is correct
24 Correct 7 ms 4228 KB Output is correct
25 Correct 6 ms 4228 KB Output is correct
26 Correct 6 ms 4228 KB Output is correct
27 Correct 6 ms 4228 KB Output is correct
28 Correct 6 ms 4228 KB Output is correct
29 Correct 6 ms 4228 KB Output is correct
30 Correct 6 ms 4228 KB Output is correct
31 Correct 6 ms 4228 KB Output is correct
32 Correct 6 ms 4272 KB Output is correct

Subtask #2
15.0 / 15.0

# Verdict Execution time Memory Grader output
1 Correct 7 ms 4280 KB Output is correct
2 Correct 10 ms 4280 KB Output is correct
3 Correct 7 ms 4300 KB Output is correct
4 Correct 12 ms 4300 KB Output is correct
5 Correct 7 ms 4300 KB Output is correct
6 Correct 7 ms 4300 KB Output is correct
7 Correct 11 ms 4300 KB Output is correct
8 Correct 7 ms 4300 KB Output is correct
9 Correct 13 ms 4300 KB Output is correct
10 Correct 12 ms 4300 KB Output is correct
11 Correct 13 ms 4300 KB Output is correct
12 Correct 12 ms 4300 KB Output is correct

Subtask #3
24.0 / 24.0

# Verdict Execution time Memory Grader output
1 Correct 17 ms 5704 KB Output is correct
2 Correct 314 ms 5704 KB Output is correct
3 Correct 17 ms 5704 KB Output is correct
4 Correct 177 ms 5704 KB Output is correct
5 Correct 476 ms 5704 KB Output is correct
6 Correct 527 ms 5704 KB Output is correct
7 Correct 510 ms 5704 KB Output is correct
8 Correct 621 ms 5704 KB Output is correct
9 Correct 641 ms 5708 KB Output is correct
10 Correct 471 ms 5708 KB Output is correct

Subtask #4
0 / 26.0

# Verdict Execution time Memory Grader output
1 Correct 157 ms 18888 KB Output is correct
2 Execution timed out 1084 ms 19016 KB Time limit exceeded
3 Halted 0 ms 0 KB -

Subtask #5
0 / 27.0

# Verdict Execution time Memory Grader output
1 Correct 610 ms 48252 KB Output is correct
2 Execution timed out 1091 ms 48300 KB Time limit exceeded
3 Halted 0 ms 0 KB -