Submission #7473440

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Source Code Expand

/**
 * code generated by JHelper
 * More info: https://github.com/AlexeyDmitriev/JHelper
 * @author
 */

#include<bits/stdc++.h>
using namespace std;
using ll=long long;
#define fr(i,n) for(int i=0;i<(n);++i)
#define Fr(i,n) for(int i=1;i<=(n);++i)
#define ifr(i,n) for(int i=(n)-1;i>=0;--i)
#define iFr(i,n) for(int i=(n);i>0;--i)

class DPairCards {
public:
    void solve(istream& in, ostream& out) {
        cin.tie(nullptr);
        ios::sync_with_stdio(false);
        int n,m,x;
        in>>n>>m;
        vector<int> y(100001),z(m),w(m);
        fr(i,n) in>>x,++y[x];
        Fr(i,100000) z[i%m]+=y[i],w[i%m]+=y[i]/2;
        int ans=z[0]/2;
        if((m&1)==0) ans+=z[m/2]/2;
        Fr(i,(m-1)/2){
            int k=min(z[i],z[m-i]);
            ans+=k;
            z[i]-=k;z[m-i]-=k;
            ans+=min(z[i]/2,w[i]);
            ans+=min(z[m-i]/2,w[m-i]);
        }
        out<<ans<<endl;
    }
};

int main() {
    DPairCards solver;
    std::istream& in(std::cin);
    std::ostream& out(std::cout);
    solver.solve(in, out);
    return 0;
}

Submission Info

Judge Result