Submission #240679

#	Time	Username	Problem	Language	Result	Execution time	Memory
240679		rqi	Palindromes (APIO14_palindrome)	C++14	73 / 100	1099 ms	88492 KiB

palindrome

#include <bits/stdc++.h>
using namespace std;
 
typedef long long ll;
typedef long double ld;
typedef double db; 
typedef string str; 

typedef pair<int,int> pi;
typedef pair<ll,ll> pl; 
typedef pair<db,db> pd; 

typedef vector<int> vi; 
typedef vector<ll> vl; 
typedef vector<db> vd; 
typedef vector<str> vs; 
typedef vector<pi> vpi;
typedef vector<pl> vpl; 
typedef vector<pd> vpd; 

#define mp make_pair
#define f first
#define s second
#define sz(x) (int)x.size()
#define all(x) begin(x), end(x)
#define rall(x) (x).rbegin(), (x).rend() 
#define rsz resize
#define ins insert 
#define ft front() 
#define bk back()
#define pf push_front 
#define pb push_back
#define eb emplace_back 
#define lb lower_bound 
#define ub upper_bound 

#define FOR(i,a,b) for (int i = (a); i < (b); ++i)
#define F0R(i,a) FOR(i,0,a)
#define ROF(i,a,b) for (int i = (b)-1; i >= (a); --i)
#define R0F(i,a) ROF(i,0,a)
#define trav(a,x) for (auto& a: x)

const int MOD = 1e9+7; // 998244353;
const int MX = 2e5+5; 
const ll INF = 1e18; 
const ld PI = acos((ld)-1);
const int xd[4] = {1,0,-1,0}, yd[4] = {0,1,0,-1}; 
mt19937 rng((uint32_t)chrono::steady_clock::now().time_since_epoch().count()); 

template<class T> bool ckmin(T& a, const T& b) { 
    return b < a ? a = b, 1 : 0; }
template<class T> bool ckmax(T& a, const T& b) { 
    return a < b ? a = b, 1 : 0; } 
int pct(int x) { return __builtin_popcount(x); } 
int bits(int x) { return 31-__builtin_clz(x); } // floor(log2(x)) 
int cdiv(int a, int b) { return a/b+!(a<0||a%b == 0); } // division of a by b rounded up, assumes b > 0 
int fstTrue(function<bool(int)> f, int lo, int hi) {
    hi ++; assert(lo <= hi); // assuming f is increasing
    while (lo < hi) { // find first index such that f is true 
        int mid = (lo+hi)/2; 
        f(mid) ? hi = mid : lo = mid+1; 
    } 
    return lo;
}

// INPUT
template<class A> void re(complex<A>& c);
template<class A, class B> void re(pair<A,B>& p);
template<class A> void re(vector<A>& v);
template<class A, size_t SZ> void re(array<A,SZ>& a);

template<class T> void re(T& x) { cin >> x; }
void re(db& d) { str t; re(t); d = stod(t); }
void re(ld& d) { str t; re(t); d = stold(t); }
template<class H, class... T> void re(H& h, T&... t) { re(h); re(t...); }

template<class A> void re(complex<A>& c) { A a,b; re(a,b); c = {a,b}; }
template<class A, class B> void re(pair<A,B>& p) { re(p.f,p.s); }
template<class A> void re(vector<A>& x) { trav(a,x) re(a); }
template<class A, size_t SZ> void re(array<A,SZ>& x) { trav(a,x) re(a); }

// TO_STRING
#define ts to_string
str ts(char c) { return str(1,c); }
str ts(bool b) { return b ? "true" : "false"; }
str ts(const char* s) { return (str)s; }
str ts(str s) { return s; }
template<class A> str ts(complex<A> c) { 
    stringstream ss; ss << c; return ss.str(); }
str ts(vector<bool> v) { 
    str res = "{"; F0R(i,sz(v)) res += char('0'+v[i]);
    res += "}"; return res; }
template<size_t SZ> str ts(bitset<SZ> b) {
    str res = ""; F0R(i,SZ) res += char('0'+b[i]);
    return res; }
template<class A, class B> str ts(pair<A,B> p);
template<class T> str ts(T v) { // containers with begin(), end()
    bool fst = 1; str res = "{";
    for (const auto& x: v) {
        if (!fst) res += ", ";
        fst = 0; res += ts(x);
    }
    res += "}"; return res;
}
template<class A, class B> str ts(pair<A,B> p) {
    return "("+ts(p.f)+", "+ts(p.s)+")"; }

// OUTPUT
template<class A> void pr(A x) { cout << ts(x); }
template<class H, class... T> void pr(const H& h, const T&... t) { 
    pr(h); pr(t...); }
void ps() { pr("\n"); } // print w/ spaces
template<class H, class... T> void ps(const H& h, const T&... t) { 
    pr(h); if (sizeof...(t)) pr(" "); ps(t...); }

// DEBUG
void DBG() { cerr << "]" << endl; }
template<class H, class... T> void DBG(H h, T... t) {
    cerr << ts(h); if (sizeof...(t)) cerr << ", ";
    DBG(t...); }
#ifdef LOCAL // compile with -DLOCAL
#define dbg(...) cerr << "LINE(" << __LINE__ << ") -> [" << #__VA_ARGS__ << "]: [", DBG(__VA_ARGS__)
#else
#define dbg(...) 0
#endif

// FILE I/O
void setIn(string s) { freopen(s.c_str(),"r",stdin); }
void setOut(string s) { freopen(s.c_str(),"w",stdout); }
void unsyncIO() { ios_base::sync_with_stdio(0); cin.tie(0); }
void setIO(string s = "") {
    unsyncIO();
    // cin.exceptions(cin.failbit); 
    // throws exception when do smth illegal
    // ex. try to read letter into int
    if (sz(s)) { setIn(s+".in"), setOut(s+".out"); } // for USACO
}



/**
 * Description: Polynomial hash for substrings with two bases.
 * Source:
    * KACTL
    * https://codeforces.com/contest/1207/submission/59309672
 * Verification: 
    * USACO Dec 17 Plat 1 (LCP :o)
    * CF Check Transcription
 */

typedef array<int,2> H; // bases not too close to ends 
uniform_int_distribution<int> BDIST(0.1*MOD,0.9*MOD);
const H base = {BDIST(rng),BDIST(rng)};
/// const T ibase = {(int)inv(mi(base[0])),(int)inv(mi(base[1]))};
H operator+(H l, H r) { 
    F0R(i,2) if ((l[i] += r[i]) >= MOD) l[i] -= MOD;
    return l; }
H operator-(H l, H r) { 
    F0R(i,2) if ((l[i] -= r[i]) < 0) l[i] += MOD;
    return l; }
H operator*(H l, H r) { 
    F0R(i,2) l[i] = (ll)l[i]*r[i]%MOD;
    return l; }
H makeH(char c) { return {c,c}; }
/// H& operator+=(H& l, H r) { return l = l+r; }
/// H& operator-=(H& l, H r) { return l = l-r; }
/// H& operator*=(H& l, H r) { return l = l*r; }

vector<H> pows = {{1,1}};
struct HashRange {
    str S; vector<H> cum = {{0,0}};
    void add(char c) { S += c; cum.pb(base*cum.bk+makeH(c)); }
    void add(str s) { trav(c,s) add(c); }
    void extend(int len) { while (sz(pows) <= len) pows.pb(base*pows.bk); }
    H hash(int l, int r) { int len = r+1-l; extend(len);
        return cum[r+1]-pows[len]*cum[l]; }
    /**int lcp(HashRange& b) { return first_true([&](int x) { 
        return cum[x] != b.cum[x]; },0,min(sz(S),sz(b.S)))-1; }*/
};

/**
 * Description: insert int, query max xor with some int in the trie
 * Time: O(MXBIT)
 * Source: CF Algorithms Gym
 * Verification: January Easy 2018 - Shubham and Subarray Xor
 */

template<int MX> struct Trie {
    map<H, int> m; //substring --> node
    int nex[MX][26], sz[MX], num = 0; // num is last node in trie

    Trie() { memset(nex,0,sizeof nex); memset(sz,0,sizeof sz); }

    ll traverse(int node, int depth, int mode){ //mode 1 --> odd, mode 2 --> even
        ll curans = 0;
        for(int i = 0; i < 26; i++){
            if(nex[node][i] == 0) continue;
            ckmax(curans, traverse(nex[node][i], depth+1, mode));
            sz[node]+=sz[nex[node][i]];
        }
        int adjust = mode-2;
        ckmax(curans, ll(sz[node])*(depth*2+adjust));
        return curans;
    }

};




int N;
string A;
HashRange h1;
HashRange h2;
Trie<300010> t1;
Trie<300010> t2;
ll ans = 0;

int main() {
    setIO();
    cin >> A;
    N = sz(A);
    h1.add(A);
    reverse(all(A));
    h2.add(A);
    reverse(all(A));
    //dbg(A);
    //Odd length palindromes
    for(int i = 0; i < N; i++){
        int lo = 0;
        int hi = min(i-0, N-1-i);
        while(lo < hi){
            int mid = (lo+hi)/2+1;

            if(h1.hash(i, i+mid) == h2.hash(N-1-i, N-1-(i-mid))){
                lo = mid;
            }
            else hi = mid-1;
        }

        int node = 0;
        int ind = i;
        int maxind = ind+lo;
        if(t1.nex[0][A[i]-'a'] != 0){
            int lo2 = 0;
            int hi2 = lo;
            while(lo2 < hi2){
                int mid2 = (lo2+hi2)/2+1;
                if(t1.m.count(h1.hash(i, i+mid2))){
                    lo2 = mid2;
                }
                else hi2 = mid2-1;
            }
            node = t1.m[h1.hash(i, i+lo2)];
            ind = i+lo2+1;
        }

        for(int j = ind; j <= maxind; j++){
            t1.nex[node][A[j]-'a'] = ++t1.num;
            node = t1.num;
            t1.m[h1.hash(i, j)] = t1.num;
        }

        t1.sz[node]++;
    }

    ckmax(ans, t1.traverse(0, 0, 1));

    //Even length palindromes
    for(int i = 0; i+1 < N; i++){ //middle right after i
        if(A[i] != A[i+1]) continue;
        int lo = 0;
        int hi = min(i-0, N-1-(i+1));

        while(lo < hi){
            int mid = (lo+hi)/2+1;
            if(h1.hash(i+1, i+1+mid) == h2.hash(N-1-i, N-1-(i-mid))){
                lo = mid;
            }
            else hi = mid-1;
        }

        int node = 0;
        int ind = i+1;
        int maxind = ind+lo;
        if(t2.nex[0][A[i+1]-'a'] != 0){
            int lo2 = 0;
            int hi2 = lo;
            while(lo2 < hi2){
                int mid2 = (lo2+hi2)/2+1;
                if(t2.m.count(h1.hash(i+1, i+1+mid2))){
                    lo2 = mid2;
                }
                else hi2 = mid2-1;
            }
            node = t2.m[h1.hash(i+1, i+1+lo2)];
            ind = i+1+lo2+1;
        }

        //dbg(i, node, ind, maxind);

        for(int j = ind; j <= maxind; j++){
            t2.nex[node][A[j]-'a'] = ++t2.num;
            node = t2.num;
            t2.m[h1.hash(i+1, j)] = t2.num;
        }

        t2.sz[node]++;
    }

    //dbg(t2.sz[1]);
    ckmax(ans, t2.traverse(0, 0, 2));

    ps(ans);

    // you should actually read the stuff at the bottom
}

/* stuff you should look for
    * int overflow, array bounds
    * special cases (n=1?)
    * do smth instead of nothing and stay organized
    * WRITE STUFF DOWN
*/

Compilation message (stderr)

palindrome.cpp: In function 'void setIn(std::__cxx11::string)':
palindrome.cpp:128:31: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result]
 void setIn(string s) { freopen(s.c_str(),"r",stdin); }
                        ~~~~~~~^~~~~~~~~~~~~~~~~~~~~
palindrome.cpp: In function 'void setOut(std::__cxx11::string)':
palindrome.cpp:129:32: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result]
 void setOut(string s) { freopen(s.c_str(),"w",stdout); }
                         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 8 / 8
• Subtask 2: 15 / 15
• Subtask 3: 24 / 24
• Subtask 4: 26 / 26
• Subtask 5: 0 / 27