Submission #1273864

#	Time	Username	Problem	Language	Result	Execution time	Memory
1273864		anbg	XOR Sum (info1cup17_xorsum)	C++20	56 / 100	1695 ms	8256 KiB

xorsum

#include<bits/stdc++.h>
using namespace std;
int n;
const int N=1e6+3;
int a[N];
int b[N];

int main()
{
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    cin>>n;
    for(int i=1;i<=n;i++)
    {
        cin>>a[i];
    }
    long long ans=0;
    for(int mask=0;mask<=30;mask++)
    {
        int   total=0;
        int  t=(1ll<<mask);
        int pos=n+1;
        for(int i=1;i<=n;i++)
        {
            b[i]=a[i]%(t<<1);
        }
        sort(b+1,b+n+1);
        for(int i=1;i<=n;i++)
        {
            if(b[i]>=t){pos=i;break;}
        }

        int ptr=0;
        for(int i=pos-1;i>0;i--)
        {
            if(ptr>i)break;
            while(ptr<=i&&b[ptr]+b[i]<t)ptr++;
           total+=(i-ptr+1);
        }
         ptr=pos;
        for(int i=pos;i<=n;i++)
        {
             while(ptr>0&&b[i]+b[ptr]>=(t<<1))ptr--;
             total+=ptr;
        }
        ptr=pos;
        for(int i=n;i>=pos;i--)
        {
            if(ptr>i)break;
            while(ptr<=i&&b[i]+b[ptr]<(t<<1)+t)ptr++;
            total+=i-ptr+1;
        }
        ans+=((total)&1)<<mask;
    }
    cout<<ans;
}

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