complementar

#include <bits/stdc++.h>

using namespace std;
ifstream fin("complementar.in");
ofstream fout("complementar.out");

int n, m, p2, a[200005];
char mat[35];
long long nr;
long long xorPairCount(int arr[], int n, int x)
{
    long long result = 0;
    unordered_map<long long, long long> mp;

    for (int i=0; i<n ; i++)
    {
        int curr_xor =  x^arr[i];
        if (mp.find(curr_xor) != mp.end())
            result += mp[curr_xor];
        mp[arr[i]]++;
    }
    return result;
}

int main()
{
    int i;
    fin>>n>>m;
    p2=(1<<m)-1;
    fin.get();
    for(i=0;i<n;i++)
    {
        fin>>mat;
        int dec_value=0;
        int base=1;
        for(int k=m-1;k>=0;k--)
        {
            dec_value+=((int)(mat[k]-'0'))*base;
            base=base*2;
        }
        a[i]=dec_value;
    }
    nr=xorPairCount(a,n,p2);
    fout<<nr;
    return 0;
}