結果

問題 No.811 約数の個数の最大化
ユーザー peroonperoon
提出日時 2019-04-19 11:40:10
言語 C++14
(gcc 12.3.0 + boost 1.83.0)
結果
AC  
実行時間 104 ms / 2,000 ms
コード長 1,585 bytes
コンパイル時間 1,726 ms
コンパイル使用メモリ 174,080 KB
実行使用メモリ 6,944 KB
最終ジャッジ日時 2024-09-22 11:22:08
合計ジャッジ時間 2,611 ms
ジャッジサーバーID
（参考情報） 		judge2 / judge5
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テストケース

テストケース表示
入力 結果 実行時間
実行使用メモリ
testcase_00 AC 2 ms
6,816 KB
testcase_01 AC 2 ms
6,940 KB
testcase_02 AC 29 ms
6,940 KB
testcase_03 AC 2 ms
6,944 KB
testcase_04 AC 2 ms
6,940 KB
testcase_05 AC 3 ms
6,940 KB
testcase_06 AC 5 ms
6,940 KB
testcase_07 AC 5 ms
6,940 KB
testcase_08 AC 14 ms
6,940 KB
testcase_09 AC 23 ms
6,940 KB
testcase_10 AC 12 ms
6,940 KB
testcase_11 AC 20 ms
6,940 KB
testcase_12 AC 8 ms
6,940 KB
testcase_13 AC 104 ms
6,940 KB
testcase_14 AC 27 ms
6,940 KB
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コンパイルメッセージ
In file included from /home/linuxbrew/.linuxbrew/Cellar/gcc@12/12.3.0/include/c++/12/istream:39,
                 from /home/linuxbrew/.linuxbrew/Cellar/gcc@12/12.3.0/include/c++/12/sstream:38,
                 from /home/linuxbrew/.linuxbrew/Cellar/gcc@12/12.3.0/include/c++/12/complex:45,
                 from /home/linuxbrew/.linuxbrew/Cellar/gcc@12/12.3.0/include/c++/12/ccomplex:39,
                 from /home/linuxbrew/.linuxbrew/Cellar/gcc@12/12.3.0/include/c++/12/x86_64-pc-linux-gnu/bits/stdc++.h:54,
                 from main.cpp:1:
In member function 'std::basic_ostream<_CharT, _Traits>::__ostream_type& std::basic_ostream<_CharT, _Traits>::operator<<(long long int) [with _CharT = char; _Traits = std::char_traits<char>]',
    inlined from 'int main()' at main.cpp:84:5:
/home/linuxbrew/.linuxbrew/Cellar/gcc@12/12.3.0/include/c++/12/ostream:202:25: warning: 'max_M' may be used uninitialized [-Wmaybe-uninitialized]
  202 |       { return _M_insert(__n); }
      |                ~~~~~~~~~^~~~~
main.cpp: In function 'int main()':
main.cpp:73:8: note: 'max_M' was declared here
   73 |     ll max_M;
      |        ^~~~~

ソースコード

diff # 

#include<bits/stdc++.h>
using namespace std;
using ll = long long;

#define FOR(i,a,b) for(ll i=(a);i<(b);++i)
#define ALL(v) (v).begin(), (v).end()
#define p(s) cout<<(s)<<endl
#define p2(s, t) cout << (s) << " " << (t) << endl
#define br() p("")
#define pn(s) cout << (#s) << " " << (s) << endl
#define p_yes() p("Yes")
#define p_no() p("No")

const ll mod = 1e9 + 7;
const ll inf = 1e18;

ll gcd(ll a,ll b){
    if(b == 0) return a;
    return gcd(b,a%b);
}

map<ll, ll> factorize(ll n){
    map<ll, ll> mp;
    ll sq = sqrt(n);
    FOR(i, 2, sq+1){
        while(n%i==0){
            mp[i]++;
            n/=i;
        }
    }
    // 残り
    if(n!=1){
        mp[n]++;
    }
    return mp;
}

// 素因数の個数 (重複あり) ex. {2, 2, 2, 3}
ll prime_factor_num(ll a){
    ll count = 0;
    auto mp = factorize(a);
    for(auto p : mp){
        count += p.second;
    }
    return count;
}

// a, bの共通の素因数の数
ll common(ll a, ll b){
    ll g = gcd(a, b);
    return prime_factor_num(g);
}

// 約数の個数
ll divisor_num(ll a){
    auto mp = factorize(a);
    ll ret = 1;
    for(auto p : mp){
        ret *= (p.second + 1);
    }
    return ret;
}

int main(){
    cin.tie(0);
    ios::sync_with_stdio(false);

    // input
    ll N, K;
    cin >> N >> K;

    ll max_divisor_num = 0;
    ll max_M;
    FOR(i, 1, N){
        if(common(i, N)>=K){
            ll div = divisor_num(i);
            if(div > max_divisor_num){
                max_divisor_num = div;
                max_M = i;
            }
        }
    }

    p(max_M);
    
    return 0;
}
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