제출 #634891

#	제출 시각	아이디	문제	언어	결과	실행 시간	메모리
634891		Son	회문 (APIO14_palindrome)	C++14	0 / 100	176 ms	17052 KiB

palindrome

#include <bits/stdc++.h>
using namespace std;
#define LL long long

string s;
char inp[300005];
int n;

int mo = 1e9 + 7;
int base = 999999937;
int p_pow[300000 * 2 + 10];
int i_pow[300000 * 2 + 10];
int pfx[300000 * 2 + 10];

int expo(int a, int b){
    if ( b == 0 ) return 1;
    int half = expo(a,b/2);
    half = ( 1LL * half * half ) % mo;
    if ( b & 1 ) half = (1LL * half * a ) % mo;
    return half;
}

int h( int l, int r ){
    int ans = pfx[r] - pfx[l];
    if ( ans < 0 ) ans += mo;
    ans = ( ans * 1LL * i_pow[l] ) % mo;
    return ans;
}

vector < int > manacher_odd(string s){
    vector < int > p(s.size(), 0);
    int l = 1, r = 1;
    for ( int i = 1; i <= s.size()-2; i++ ){
        p[i] = max(0, min(r-i, p[l + (r-i)]) );
        while ( s[i-p[i]] == s[i+p[i]] ){
            p[i]++;
        } 
        if ( i + p[i] > r ){
            l = i - p[i];
            r = i + p[i];
        }
    }
    return p;
}

LL solve1(){
    s = inp;
    s = "$" + s + "^";
    vector < int > p = manacher_odd(s);

    int N = s.size() - 2;

    for ( int i = 0; i < s.size(); i++ ){
        pfx[i] = (s[i] * 1LL * p_pow[i]) % mo;
        if ( i ) pfx[i] += pfx[i-1];
        if ( pfx[i] >= mo ) pfx[i] -= mo;
    }

    map < int , int > occ;
    LL ans = 0;
    for ( int i = 1; i <= N; i++ ){
        int l = i - p[i], r = i + p[i];
        ans = max( ans, (++occ[h(l,r-1)]) * 1LL * (p[i] * 2 - 1) );
    }
    return ans;
}

LL solve2(){
    s = "$";
    for ( int i = 0; i < n; i++ ){
        s += "#";
        s += inp[i];
    }
    s += "#^";
    vector < int > p = manacher_odd(s);

    int N = s.size()-2;

    for ( int i = 0; i < s.size(); i++ ){
        pfx[i] = (s[i] * 1LL * p_pow[i]) % mo;
        if ( i ) pfx[i] += pfx[i-1];
        if ( pfx[i] >= mo ) pfx[i] -= mo;
    }

    LL ans = 0;
    map < int , int > occ;
    for ( int i = 1; i <= N; i++ ){
        if ( s[i] == '#' ){
            int l = i - p[i], r = i + p[i];
            ans = max( ans, (++occ[h(l,r-1)]) * 1LL * (p[i] - 1));
        }   
    }

    return ans;
}

int main(){

    scanf("%s",&inp);
    n = strlen(inp);
    
    int p = 1;
    for ( int i = 0; i <= (n + 3) * 2; i++ ){
        p_pow[i] = p;
        p = (p * 1LL * base) % mo;
    }
    int inv = expo(base,mo-2);
    int ip = 1;
    for ( int i = 0; i <= (n+3) * 2 ; i++ ){
        i_pow[i] = ip;
        ip = (1LL * ip * inv) % mo;
    }

    LL ans1 = solve1();
    LL ans2 = solve2();
    if ( ans1 > ans2 ) printf("%lld\n",ans1);
    else printf("%lld\n",ans2);
    return 0;
}

컴파일 시 표준 에러 (stderr) 메시지

palindrome.cpp: In function 'std::vector<int> manacher_odd(std::string)':
palindrome.cpp:33:24: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   33 |     for ( int i = 1; i <= s.size()-2; i++ ){
      |                      ~~^~~~~~~~~~~~~
palindrome.cpp: In function 'long long int solve1()':
palindrome.cpp:53:24: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   53 |     for ( int i = 0; i < s.size(); i++ ){
      |                      ~~^~~~~~~~~~
palindrome.cpp: In function 'long long int solve2()':
palindrome.cpp:79:24: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   79 |     for ( int i = 0; i < s.size(); i++ ){
      |                      ~~^~~~~~~~~~
palindrome.cpp: In function 'int main()':
palindrome.cpp:99:13: warning: format '%s' expects argument of type 'char*', but argument 2 has type 'char (*)[300005]' [-Wformat=]
   99 |     scanf("%s",&inp);
      |            ~^  ~~~~
      |             |  |
      |             |  char (*)[300005]
      |             char*
palindrome.cpp:99:10: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   99 |     scanf("%s",&inp);
      |     ~~~~~^~~~~~~~~~~

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