Submission #250638

#	Time	Username	Problem	Language	Result	Execution time	Memory
250638		Sorting	Palindromic Partitions (CEOI17_palindromic)	C++14	60 / 100	10094 ms	21644 KiB

palindromic

#include <bits/stdc++.h>

using namespace std;

typedef long long ll;

const int k_N = 1e6 + 3;
const int cnt_Mod = 1;
const array<ll, cnt_Mod> k_Mod{(int)1e9 + 7}, k_Base{293};

int dp[k_N];
string s;
int n;

array<ll, cnt_Mod> h[k_N], b_pow[k_N];
vector<int> pos[256];
int idx[256];

ll get_hash(int l, int r, int idx){
    if(l == 0) return h[r][idx];
    ll ans = (h[r][idx] - h[l - 1][idx] * b_pow[r - l + 1][idx]) % k_Mod[idx];
    return (ans < 0) ? (ans + k_Mod[idx]) : ans;
}

bool equal(int l1, int r1, int l2, int r2){
    for(int i = 0; i < cnt_Mod; ++i)
        if(get_hash(l1, r1, i) != get_hash(l2, r2, i))
            return false;
    return true;
}

void init_hashing(){
    for(int i = 0; i < n; ++i){
        for(int j = 0; j < cnt_Mod; ++j){
            if(i == 0)
                h[i][j] = s[i];
            else
                h[i][j] = (h[i - 1][j] * k_Base[j] + s[i]) % k_Mod[j];
        }
    }

    for(int i = 0; i < n; ++i){
        for(int j = 0; j < cnt_Mod; ++j){
            if(i == 0)
                b_pow[i][j] = 1;
            else
                b_pow[i][j] = b_pow[i - 1][j] * k_Base[j] % k_Mod[j];
        }
    }
}

void solve(){
    cin >> s;
    n = (int)s.size();

    if(n == 1){
        cout << "1\n";
        return;
    }


    init_hashing();
    for(int i = 0; i < n; ++i)
        pos[s[i]].push_back(i);

    int mid = (n - 1) / 2, mid2 = (n - 2) / 2;
    dp[mid + 1] = 0;
    for(int i = mid; i >= 0; --i){
        dp[i] = 1;
        for(int k = (int)pos[s[i]].size() - 1; k >= 0; --k){
            int j = pos[s[i]][k];
            if(j > n - i - 1) continue;
            if(n - j - 1 >= j) break;
            
            if(dp[n - j] + 2 <= dp[i]) break;

            if(equal(i, n - j - 1, j, n - i - 1))
                dp[i] = max(dp[n - j] + 2, dp[i]);
        }
    }

    cout << dp[0] << "\n";
}

int main(){
    ios::sync_with_stdio(false);
    cin.tie(NULL);

    int t;
    cin >> t;

    while(t--)
        solve();
}

Compilation message (stderr)

palindromic.cpp: In function 'void solve()':
palindromic.cpp:64:17: warning: array subscript has type 'char' [-Wchar-subscripts]
         pos[s[i]].push_back(i);
                 ^
palindromic.cpp:70:34: warning: array subscript has type 'char' [-Wchar-subscripts]
         for(int k = (int)pos[s[i]].size() - 1; k >= 0; --k){
                                  ^
palindromic.cpp:71:29: warning: array subscript has type 'char' [-Wchar-subscripts]
             int j = pos[s[i]][k];
                             ^
palindromic.cpp:66:28: warning: unused variable 'mid2' [-Wunused-variable]
     int mid = (n - 1) / 2, mid2 = (n - 2) / 2;
                            ^~~~

• Subtask 1: 15 / 15
• Subtask 2: 20 / 20
• Subtask 3: 25 / 25
• Subtask 4: 0 / 40