Submission #864337

#	Time	Username	Problem	Language	Result	Execution time	Memory
864337		VN_AnhTuan	Palinilap (COI16_palinilap)	C++14	54 / 100	23 ms	8796 KiB

palinilap

#include <bits/stdc++.h>

#define fi first
#define se second
#define pii pair<int, int>
#define mp make_pair
#define pb push_back
#define bit(X,i) ((X>>i)&1)
#define fori(i,d,c) for(int i = d; i <= c; ++ i)
#define ford(i,d,c) for(int i = d; i >= c; -- i)
#define all(V) V.begin(), V.end()
#define RRH(V) V.resize(unique(all(V))-V.begin())
#define Task "palival"

using namespace std;
using ll = long long;
using ld = long double;

const int maxn = 1e5 + 5;
const int maxm = 1e6 + 5;
const int base = 101;

string s, BASE_STRING;
int n;

void read() {
    cin >> s;
    BASE_STRING = s;
    n = s.size();
    s = " " + s;
}

namespace sub1{
    int f[105][105];
    int calc() {
        ford(i,n,1) {
            fori(j,i,n) {
                if (j == i) f[i][j] = 1;
                else {
                    if (s[i] == s[j]) {
                        if (i + 1 == j) f[i][j] = 1;
                        else f[i][j] = f[i+1][j-1];
                    }
                    else f[i][j] = 0;
                }
            }
        }
        int res = 0;
        fori(i,1,n) fori(j,i,n) res += f[i][j];
        return res;
    }
    void solve() {
        int res = calc();
        fori(i,1,n) {
            char c = s[i];
            fori(j,0,25) {
                if (s[i] - 'a' == j) continue;
                s[i] = char(j + 'a');
//                if(calc() > res) {
//                    cout << i << ' ' << s[i] << '\n';
//                }
                res = max(res, calc());
            }
            s[i] = c;
        }
        cout << res;
    }
}

ll Total_Result;

namespace tester {
    int f[5005][5005];
    int calc() {
        ford(i,n,1) {
            fori(j,i,n) {
                if (j == i) f[i][j] = 1;
                else {
                    if (s[i] == s[j]) {
                        if (i + 1 == j) f[i][j] = 1;
                        else f[i][j] = f[i+1][j-1];
                    }
                    else f[i][j] = 0;
                }
            }
        }
        int res = 0;
        fori(i,1,n) fori(j,i,n) res += f[i][j];
        return res;
    }
    void solve() {
        int cs = -1, sum = 0;
        fori(i,2,n-1) {
            if (s[i-1] == s[i+1]) {
                int j = i-1;
                while(j - 1 >= 1 && s[j-1] == s[j]) j --;
                int j1 = i+1;
                while(j1 + 1 <= n && s[j1 + 1] == s[j1]) j1 ++;
                if (j1 - j + 1 > sum) {
                    cs = i;
                    sum = j1 - j + 1;
                }
            }
        }
        int res = calc();
        if (1){
            int sum1 = 0;
            int cs1 = 0, cs2 = n + 1;
            for(int i = 1; i <= n;) {
                int j1 = i;
                while(j1 + 1 <= n && s[j1 + 1] == s[i]) j1 ++;
                if (sum1 < j1 - i + 1) {
                    sum1 = j1 - i + 1;
                    cs1 = i - 1;
                    cs2 = j1 + 1;
                }
                i = j1 + 1;
            }
            if (cs1 >= 1) {
                char c = s[cs1];
                s[cs1] = s[cs1 + 1];
                res = max(res, calc());
                s[cs1] = c;
            }
            if (cs2 <= n) {
                char c = s[cs2];
                s[cs2] = s[cs2-1];
                res = max(res, calc());
                s[cs2] = c;
            }
            Total_Result = max(Total_Result, 1ll * res);
        }
        if (cs != -1){
            s[cs] = s[cs-1];
            res = max(res, calc());
            Total_Result = max(Total_Result, 1ll * res);
        }
    }
}

namespace sub2 {

    #define FOR(i, a, b) for(int i = (a); i < (b); ++i)
    #define REP(i, n) FOR(i, 0, n)
    #define TRACE(x) cerr << #x << " = " << x << endl
    #define _ << " " <<

    typedef pair<int, int> point;

    const ll MOD = 1e9 + 7;
    const ll BAZA = 1307;

    string s;
    int h[maxn], h_[maxn], pot[maxn];

    void calcHash(){
        pot[0] = 1;
        h[0] = s[0];

        FOR(i, 1, (int)s.size()){
            h[i] = ((ll)h[i - 1] * BAZA + s[i]) % MOD;
            pot[i] = (ll)pot[i - 1] * BAZA % MOD;
        }

        h_[0] = s[s.size() - 1];
        for(int i = s.size() - 2, cnt = 1; i >= 0; --i, ++cnt)
            h_[cnt] = ((ll)h_[cnt - 1] * BAZA + s[i]) % MOD;
    }

    ll calc(ll x, ll y){
        ll k = 0;
        if(x) k = (ll)h[x - 1] * pot[y] % MOD;
        return ((((ll)h[x + y - 1] - k) % MOD) + MOD) % MOD;
    }

    ll calc_(ll x, ll y){
        ll k = 0;
        if(x) k = (ll)h_[x - 1] * pot[y] % MOD;
        return ((((ll)h_[x + y - 1] - k) % MOD) + MOD) % MOD;
    }

    ll cntDec[maxn];
    ll decrease[maxn];
    ll increase[maxn], letInc[maxn][30];

    void solve(){
        ios_base::sync_with_stdio(false); cin.tie(0),

        s = BASE_STRING;

        calcHash();
        ll sol = 0;

        int len = s.size();

        REP(i, len){
            //neparni
            ll lo = 1, hi = min(i + 1, len - i);
            while(lo < hi){
                ll mid = (lo + hi + 1) >> 1;
                /*if(i + mid - 1 >= s.size() || len - i - 1 + mid - 1 >= s.size()){
                    assert(s.size() == 0);
                }*/

                if(calc(i, mid) == calc_(len - i - 1, mid))
                    lo = mid;
                else
                    hi = mid - 1;
            }

            cntDec[i - lo + 1] ++;
            cntDec[i + 1] -= 2;
            cntDec[i + lo + 1] ++;

            sol += lo;
            increase[i] += lo;

            ll jump = lo + 1;
            lo = 0, hi = max(0LL, min(i + 1, len - i) - jump);
            while(lo < hi){
                ll mid = (lo + hi + 1) >> 1;
                /*if(i + jump + mid - 1 >= s.size() || len - i + jump - 1 + mid - 1 >= s.size()){
                    assert(s.size() == 0);
                }*/
                if(calc(i + jump, mid) == calc_(len - i + jump - 1, mid))
                    lo = mid;
                else
                    hi = mid - 1;
            }

            letInc[i + jump - 1][s[i - jump + 1] - 'a'] += lo + 1;
            letInc[i - jump + 1][s[i + jump - 1] - 'a'] += lo + 1;

            if(i == len - 1) continue;
            //neparni
            lo = 0, hi = max(0, min(i + 1, len - i - 1));
            while(lo < hi){
                ll mid = (lo + hi + 1) >> 1;
                /*if(i + 1 + mid - 1 >= s.size() || len - i - 1 - mid + 1 >= s.size()){
                    assert(s.size() == 0);
                }*/
                if(calc(i + 1, mid) == calc_(len - i - 1, mid))
                    lo = mid;
                else
                    hi = mid - 1;
            }

            sol += lo;

            if(lo){
                cntDec[i - lo + 1] ++;
                cntDec[i + 1] --;
                cntDec[i + 2] --;
                cntDec[i + lo + 2] ++;
            }

            jump = lo + 1;
            lo = 0, hi = max(0LL, min(i + 1, len - i - 1) - jump);
            while(lo < hi){

                ll mid = (lo + hi + 1) >> 1;
                /*if(i + jump + 1 + mid - 1 >= s.size() || len - i + jump - 1 + mid - 1 >= s.size()){
                    assert(s.size() == 0);
                }*/
                if(calc(i + jump + 1, mid) == calc_(len - i + jump - 1, mid))
                    lo = mid;
                else
                    hi = mid - 1;
            }

            letInc[i + jump][s[i - jump + 1] - 'a'] += lo + 1;
            letInc[i - jump + 1][s[i + jump] - 'a'] += lo + 1;
        }

        ll cnt = 0, curr = 0;

        REP(i, len){
            cnt += cntDec[i];
            curr += cnt;
            decrease[i] = curr;
        }

        ll best = 0;
        REP(i, len)
            REP(j, 26){
                best = max(best, increase[i] + letInc[i][j] - decrease[i]);

            }

        cout << sol + best;
    }
}

void solve() {
    Total_Result = n;
    if (n <= 100) sub1::solve();
    else if (n <= 5000)
        sub2::solve();
    else {
        tester::solve();
        cout << Total_Result;
    }
}

int main () {
    ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
    if (fopen(Task".inp", "r")) {
        freopen(Task".inp", "r", stdin);
        freopen(Task".out", "w", stdout);
    }
    read();
    solve();
    cerr << "\nTime elapsed: " << 1000 * clock() / CLOCKS_PER_SEC << "ms\n";
    return 0;
}

Compilation message (stderr)

palinilap.cpp: In function 'int main()':
palinilap.cpp:308:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  308 |         freopen(Task".inp", "r", stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
palinilap.cpp:309:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  309 |         freopen(Task".out", "w", stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 17 / 17
• Subtask 2: 37 / 37
• Subtask 3: 0 / 46