코드 복사/붙여넣기 하는 당신이 아름답습니다.

1067 : 이동

풀이

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코드

#define _USE_MATH_DEFINES
#include <cstdio>
#include <cmath>
#include <complex>
#include <vector>
#include <algorithm>
using namespace std;
 
#define sz(v) ((int)(v).size())
#define all(v) (v).begin(),(v).end()
typedef complex<double> base;
 
void fft(vector<base> &a, bool invert) {
    int n = sz(a);
    for (int i=1,j=0;i<n;i++){
        int bit = n >> 1;
        for (;j>=bit;bit>>=1) j -= bit;
        j += bit;
        if (i < j) swap(a[i],a[j]);
    }
    for (int len=2;len<=n;len<<=1){
        double ang = 2*M_PI/len*(invert?-1:1);
        base wlen(cos(ang),sin(ang));
        for (int i=0;i<n;i+=len){
            base w(1);
            for (int j=0;j<len/2;j++){
                base u = a[i+j], v = a[i+j+len/2]*w;
                a[i+j] = u+v;
                a[i+j+len/2] = u-v;
                w *= wlen;
            }
        }
    }
    if (invert) {
        for (int i=0;i<n;i++) a[i] /= n;
    }
}
 
void multiply(const vector<int> &a,const vector<int> &b,vector<int> &res) {
    vector <base> fa(all(a)), fb(all(b));
    int n = 1;
    while (n < max(sz(a),sz(b))) n <<= 1;
    fa.resize(n); fb.resize(n);
    fft(fa,false); fft(fb,false);
    for (int i=0;i<n;i++) fa[i] *= fb[i];
    fft(fa,true);
    res.resize(n);
    for (int i=0;i<n;i++) res[i] = int(fa[i].real()+(fa[i].real()>0?0.5:-0.5));
}


int main() {
    int n;
    vector<int> a, b, res;
    scanf("%d", &n);
    a.resize(n*2); b.resize(n);
    for (int i=0;i<n;i++) {
        scanf("%d", &a[i]);
        a[i+n] = a[i];
    }
    for (int i=0;i<n;i++) {
        scanf("%d", &b[n-i-1]);
    }

    multiply(a, b, res);

    int ans = 0;
    for (int i=n;i<n*2;i++) {
        ans = max(ans, res[i]);
    }

    printf("%d", ans);

    return 0;
}

아무말

백준, 백준 온라인 저지, BOJ, Baekjoon Online Judge, C, C++, 씨, 씨쁠쁠, JAVA, algorithm, 자바, 알고리즘, 자료구조, 문제, 문제 풀이, 풀이

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wookje.kwon

2018-06-30 09:21

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