Submission #1019234

#	Time	Username	Problem	Language	Result	Execution time	Memory
1019234		stefanopulos	Palinilap (COI16_palinilap)	C++17	100 / 100	104 ms	44892 KiB

palinilap

#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
#include <bits/stdc++.h>
 
using namespace std;
using namespace __gnu_pbds;
 
typedef long long ll;
typedef long double ldb;
 
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;
typedef pair<ldb,ldb> pdd;

#define ff(i,a,b) for(int i = a; i <= b; i++)
#define fb(i,b,a) for(int i = b; i >= a; i--)
#define trav(a,x) for(auto& a : x)
 
#define sz(a) (int)(a).size()
#define fi first
#define se second
#define pb push_back
#define lb lower_bound
#define ub upper_bound
#define all(a) a.begin(), a.end()
#define rall(a) a.rbegin(), a.rend()
 
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());

template<typename T>
using ordered_set = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;

// os.order_of_key(k) the number of elements in the os less than k
// *os.find_by_order(k)  print the k-th smallest number in os(0-based)

const int mod = 1000000007;
const int inf = 1e9 + 5;
const int mxN = 200005; 

int n;
string s;

int d1[mxN];
int d2[mxN];
void manacher(string a){
    int N = sz(a);
    int L = 0, R = -1;
    ff(i,0,N - 1){
        int j = (i > R ? 1 : min(d1[L + R - i], R - i + 1));
        while(i >= j && i + j < N && a[i - j] == a[i + j])j += 1;
        d1[i] = j--;
        if(i + j > R){
            L = i - j;
            R = i + j;
        }
    }
    
    L = 0, R = -1;
    ff(i,0,N - 1){
        int j = (i > R ? 0 : min(d2[L + R - i + 1], R - i + 1));
        while(i > j && i + j < N && a[i - j - 1] == a[i + j])j += 1;
        d2[i] = j--;
        if(i + j > R){
            L = i - j - 1;
            R = i + j;
        }
    }
    
}

ll kol[mxN];
vector<int> L1[mxN];
vector<int> R1[mxN];
vector<int> L2[mxN];
vector<int> R2[mxN];

vector<int> in[mxN];

int add(int a, int b){ a += b; if(a >= mod)a -= mod; return a; }
int sub(int a, int b){ a -= b; if(a < 0)a += mod; return a; }
int mul(int a, int b){ return (1ll * a * b) % mod; }
int power(int a, int b){
    if(!b)return 1;
    int p = power(a, b / 2);
    p = mul(p, p);
    if(b % 2 == 1)p = mul(p, a);
    return p;
}
int inv(int a){
    return power(a, mod - 2);
}

const int p1 = 37;
int pw[mxN];
int invz[mxN];

int pref[mxN];
int getP(int l, int r){
    return mul(sub(pref[r], (l == 0 ? 0 : pref[l - 1])), invz[l]); 
}

int sufi[mxN];
int getS(int l, int r){
    return mul(sub(sufi[l], sufi[r + 1]), invz[n - r - 1]); 
}

int calc(int a, int b ){

    int l = 1, r = n, ans = 0;
    while(l <= r){
        int mid = (l + r) / 2;
        if(a - mid + 1 >= 0 && b + mid - 1 < n && getP(a - mid + 1, a) == getS(b, b + mid - 1)){
            ans = mid;
            l = mid + 1;
        }
        else r = mid - 1;
    }

    return ans;

}

int main(){
    cin.tie(0)->sync_with_stdio(0);

    cin >> s; n = sz(s);

    pw[0] = 1;
    ff(i,1,n)pw[i] = mul(pw[i - 1], p1);

    invz[n] = inv(pw[n]);
    fb(i,n - 1,0)invz[i] = mul(invz[i + 1], p1);

    ff(i,0,n - 1)pref[i] = add((i == 0 ? 0 : pref[i - 1]), mul(s[i] - 'a' + 1, pw[i]));
    fb(i,n - 1,0)sufi[i] = add(sufi[i + 1], mul(s[i] - 'a' + 1, pw[n - i - 1]));

    manacher(s);

    ll uk = 0;
    ff(i,0,n - 1)uk += d1[i] + d2[i];

    ff(i,0,n - 1){
        L1[i + d1[i] - 1].pb(i);
        L2[i + d2[i] - 1].pb(i); 

        R1[i - d1[i] + 1].pb(i); 
        R2[i - d2[i]].pb(i); 

        kol[i] = uk;
    }


    ll sum = 0, br = 0;
    ff(i,0,n - 1){
        if(d2[i] > 0){
            in[i + d2[i] - 1].pb(i + d2[i]); sum += (i + d2[i]); br += 1;
        }
        
        kol[i] += 1ll * br * i - sum;

        in[i + d1[i] - 1].pb(i + d1[i]); sum += (i + d1[i]); br += 1;
        for(auto c : in[i]){
            sum -= c; br -= 1;
        }

        in[i].clear();

    }

    sum = 0, br = 0;
    fb(i,n - 1,0){
        kol[i] += sum - 1ll * br * i;

        in[i - d1[i] + 1].pb(i - d1[i]); sum += (i - d1[i]); br += 1;
        if(d2[i] > 0){
            in[i - d2[i]].pb(i - 1 - d2[i]); sum += (i - 1 - d2[i]); br += 1;
        }

        for(auto c : in[i]){
            sum -= c; br -= 1;
        }

    }
    
    ff(i,0,n - 1){

        char old = s[i]; ll mx = 0;
        for(char a = 'a'; a <= 'z'; a++){
            if(old == a)continue;
            
            s[i] = a; ll cur = 0;

            for(auto j : L1[i - 1]){
                int l = 2 * j - i, r = i;
                if(0 <= l && l < n && 0 <= r && r < n && l <= r && s[l] == s[r]){
                    l -= 1; r += 1;
                    cur += 1 + calc(l, r);
                    
                }
            }

            for(auto j : L2[i - 1]){
                int l = 2 * j - i - 1, r = i;
                if(0 <= l && l < n && 0 <= r && r < n && l <= r && s[l] == s[r]){
                    l -= 1; r += 1;
                    cur += 1 + calc(l, r);
                }
            }
            
            for(auto j : R1[i + 1]){
                int l = i, r = 2 * j - i;
                if(0 <= l && l < n && 0 <= r && r < n && l <= r && s[l] == s[r]){
                    l -= 1; r += 1;
                    cur += 1 + calc(l, r);
                }
            }

            for(auto j : R2[i + 1]){
                int l = i, r = 2 * j - i - 1;
                if(0 <= l && l < n && 0 <= r && r < n && l <= r && s[l] == s[r]){
                    l -= 1; r += 1;
                    cur += 1 + calc(l, r);
                }
            }

            mx = max(mx, cur);

        }

        s[i] = old; kol[i] += mx;

    }

    ll rez = uk;
    ff(i,0,n - 1)rez = max(rez, kol[i]);
    cout << rez << '\n';

    return 0;
}
/*



// probati bojenje sahovski
*/
 
 
 
 
 

• Subtask 1: 17 / 17
• Subtask 2: 37 / 37
• Subtask 3: 46 / 46