Submission #3448417

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Source Code Expand

#include <bits/stdc++.h>
#include <unordered_set>
using namespace std;
#define ll long long
#define rep(i,n) for(int (i)=0;(i)<(n);(i)++)
#define repeat(i,s,n) for(int (i)=s; (i)<(n); (i)++)

ll comb(ll n, ll k) {
//  if(k==n) return 1;
  ll ret=1;
  for(ll i=n; i>=n-k+1; i--) {
    ret*=i;
  }
  for(ll i=1; i<=k; i++) {
    ret/=i;
  }
  return ret;
}

ll aCb(ll a, ll b) {
  if(b==0 || a==b) return 1;
  return aCb(a-1,b-1)+aCb(a-1,b);
}

ll po(ll b, ll e) {
  if(e==0) return 1;
  if(e%2==0) {
    ll t = po(b,e/2);
    return t*t;
  }
  return b*po(b,e-1);
}

int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  cout<<setprecision(std::numeric_limits<float>::max_digits10);
  ll n,p;
  //cout << comb(10,10) << endl;
  // rep(i,5) {
  //   rep(j,i+1) {
  //     cout << "comb(" << i << "," << j <<")=" <<comb(i,j) << endl;
  //   }
  // } 
  cin>>n>>p;
  vector<ll> a(n);
  rep(i,n) cin>>a[i];
  ll o=0,e=0;
  rep(i,n) {
    if(a[i]%2==0) {
      e++;
    } else o++;
  }
  ll ans=0;
  for(ll k=p; k<=o; k+=2) {
    // ans+=comb(o,k);
    ans+=aCb(o,k);
  }
  cout << ans*po(2,e) << endl;
  return 0;
}

Submission Info

Judge Result