1879D - Sum of XOR Functions - CodeForces Solution

#include <bits/stdc++.h>
using namespace std;
    
#ifndef ONLINE_JUDGE
#include "debug.hpp"
#else
#define debug(...) 8
#endif
    
typedef long long        ll;
#define f(i, x, n)       for (ll i = x; i < n; i++)
#define rf(i, x, n)      for (ll i = x; i >= n; i--)
#define fr(x,ds)         for(auto &x : ds)
#define pb               push_back
#define all(x)           (x).begin(), (x).end()
    
const ll mod = 998244353;
const ll inf = 1e18;
const ll N = 1e5+5;
    
void solve(){
    ll n;
    cin>>n;
    vector<ll> a(n);
    f(i,0,n) cin>>a[i];
    ll ans=0;
    f(i,0,30) {
        bool ev=0;
        ll even=-1,odd=0;
        ll evencnt=1,oddcnt=0;
        ll sum=0;
        f(j,0,n) {
            if((1ll<<i)&a[j]) {
                ev^=1;
            }
            if(!ev) {
                even+=j;
                evencnt++;
            }
            else {
                odd+=j;
                oddcnt++;
            }
            if(ev) {
                sum+=j*evencnt-even;
            }
            else {
                sum+=j*oddcnt-odd;
            }
        }
        ll tmp=(sum%mod)*((1ll<<i)%mod)%mod;
        ans=(ans+tmp)%mod;
    }
    cout<<ans<<'\n';
}
    
signed main() {
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    ll t = 1;
    // cin >> t;
    for (ll T = 1; T <= t; T++) {
        // cout << "Case #" << T << ": ";
        solve();
    }
    return 0;
}