[BOJ] 10531 : Golf Bot

#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;
    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 n, m, x, ans;
vector<int> a(200001), res;

int main() {
    scanf("%d", &n);
    for (int i = 0; i < n; i++) {
        scanf("%d", &x);
        a[x] = 1;
    }
    a[0] = 1;

    multiply(a, a, res);

    scanf("%d", &m);
    for (int i = 0; i < m; i++) {
        scanf("%d", &x);
        if (x < res.size() && res[x]) ans++;
    }

    printf("%d", ans);

    return 0;
}