Submission #517287

#	Time	Username	Problem	Language	Result	Execution time	Memory
517287		Ronin13	XOR Sum (info1cup17_xorsum)	C++14	77 / 100	1656 ms	45652 KiB

xorsum

#include<bits/stdc++.h>
#define ll long long
#define ull unsigned ll
#define pb push_back
#define epb emplace_back
#define pii pair<int,int>
#define pll pair<ll,ll>
#define f first
#define s second
#define inf 1e9+1
#define linf 1e18+1
using namespace std;

main(){
    int n;cin>>n;
    ios_base::sync_with_stdio(false);cin.tie(0);
    int a[n+1];
    int mx=0;

    for(int i=1;i<=n;i++){
        cin>>a[i];
        mx=max(mx,a[i]);
    }
    int ans=0;
    int vec[n];
    if(mx<=1e6){
        int pref[8*mx+1];
        int xx=log2(mx)+2;
        for(int bt=1;bt<=xx;bt++){
            for(int i=0;i<n;i++){
                vec[i]=a[i+1]%(1<<bt);
            }
            for(int j=0;j<=8*mx;j++)pref[j]=0;
            for(int i=0;i<n;i++){
                pref[vec[i]]++;
            }
            for(int i=1;i<=8*mx;i++)pref[i]+=pref[i-1];
            int cnt=0;
            int l=(1<<(bt-1));int r=2*l;
            for(int i=0;i<n;i++){
                int to=vec[i];
                if(2*to>=l&&2*to<r)cnt++;
                if(2*to>=r+l)cnt++;
                cnt+=pref[r-to-1];
                if(l>to)cnt-=pref[l-to-1];
                cnt+=pref[8*mx];
                if(r+l>to)cnt-=pref[r+l-to-1];
            }
            cnt>>=1;
            if(cnt&1)ans+=(1<<(bt-1));
        }
        cout<<ans<<"\n";
        return 0;
    }
    mx=log2(mx);
    for(int bt=1;bt<=mx+2;bt++){

        for(int i=0;i<n;i++){
            vec[i]=a[i+1]%(1<<bt);

        }
        sort(vec,vec+n);
        int cnt=0;
        int l=(1<<(bt-1)),r=2*l;
        for(int i=0;i<n;i++){
            int to=vec[i];
            if(2*to>=l&&2*to<r)cnt++;
            if(2*to>=r+l)cnt++;
            cnt+=lower_bound(vec,vec+n,r-to)-lower_bound(vec,vec+n,l-to);
            cnt+=vec+n-lower_bound(vec,vec+n,r+l-to);
        }
        cnt>>=1;
        if(cnt&1)ans+=(1<<(bt-1));
    }
    cout<<ans;
    return 0;
}

Compilation message (stderr)

xorsum.cpp:15:1: warning: ISO C++ forbids declaration of 'main' with no type [-Wreturn-type]
   15 | main(){
      | ^~~~

• Subtask 1: 7 / 7
• Subtask 2: 11 / 11
• Subtask 3: 21 / 21
• Subtask 4: 38 / 38
• Subtask 5: 0 / 23