Submission #766211

#	Time	Username	Problem	Language	Result	Execution time	Memory
766211		Ahmed57	XOR Sum (info1cup17_xorsum)	C++17	100 / 100	1458 ms	21580 KiB

xorsum

#pragma GCC optimize("Ofast")
#include <bits/stdc++.h>

using namespace std;

signed main(){
    ios_base::sync_with_stdio(false);cin.tie(0);
    int n;
    cin>>n;
    int arr[n];
    for(int i = 0;i<n;i++){
        cin>>arr[i];
    }
    sort(arr,arr+n);
    long long all = 0;
    reverse(arr,arr+n);
    for(int i = 0;i<=6;i++){
        long long frq[(1<<(i+1))] = {0};
        long long cnt = 0;
        for(int j = 0;j<n;j++){
            frq[arr[j]&((1<<(i+1))-1)]++;
        }
        for(int j = 0;j<(1<<(i+1));j++){
            for(int e = j;e<(1<<(i+1));e++){
                if((j+e)&(1<<i)){
                    if(j==e)cnt+=(frq[j]*frq[e]+frq[j])/2;
                    else cnt+=frq[j]*frq[e];
                }
            }
        }
        if(cnt&1)all+=(1<<i);
    }
    for(int i = 7;i<30;i++){
        vector<int> v;
        long long ans = 0;
        for(int j = 0;j<n;j++){
            if((arr[j]+arr[j])&(1LL<<i)){
                ans++;
            }
            v.push_back(arr[j]&((1LL<<(i+1))-1));
        }
        sort(v.begin(),v.end());
        int il = 0 , ir = 0;
        int ll = 0;
        for(int j = v.size()-1;j>=0;j--){
            long long l=(1LL<<i),r=(1LL<<(i+1));
            l-=v[j] , r-=v[j];
            if(l<0){
            l%=((1LL<<(i+1)));
            l+=(1LL<<(i+1));
            l&=((1LL<<(i+1))-1);
            }
            while(ir<v.size()&&v[ir]<r)ir++;
            if(l>=ll){
                while(il<v.size()&&v[il]<l)il++;
            }else{
                il = 0;
                while(il<v.size()&&v[il]<l)il++;
            }
            //cout<<l<<" "<<r<<" "<<il<<" "<<ir<<" "<<v[il]<<" "<<v[ir]<<endl;
            ll = l;
            if(l<=r)ans+=(ir-il);
            else ans+=ir+(n-il);
        }
        //cout<<endl;
        if(((ans/2)&1))all+=(1LL<<i);
    }
    cout<<all<<endl;
}

Compilation message (stderr)

xorsum.cpp: In function 'int main()':
xorsum.cpp:53:21: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   53 |             while(ir<v.size()&&v[ir]<r)ir++;
      |                   ~~^~~~~~~~~
xorsum.cpp:55:25: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   55 |                 while(il<v.size()&&v[il]<l)il++;
      |                       ~~^~~~~~~~~
xorsum.cpp:58:25: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   58 |                 while(il<v.size()&&v[il]<l)il++;
      |                       ~~^~~~~~~~~

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