Submission #215959

#	Time	Username	Problem	Language	Result	Execution time	Memory
215959		wendy_virgo	XOR Sum (info1cup17_xorsum)	C++14	45 / 100	1419 ms	33940 KiB

xorsum

#include <bits/stdc++.h>

using namespace std;

template<typename TH>
void _dbg(const char* sdbg, TH h)
{
	cerr << sdbg << " = " << h << "\n";
}

template<typename TH, typename... TA>
void _dbg(const char* sdbg, TH h, TA... t)
{
	while (*sdbg != ',') cerr << *sdbg++;
	cerr << " = " << h << ",";
	_dbg(sdbg + 1, t...);
}

#define db(...) _dbg(#__VA_ARGS__, __VA_ARGS__)
#define chkpt cerr << "--- Checkpoint here ---\n";

const int N=1e6+6;

int n;
int64_t a[N],b[N];

void Sub1(){
    int ans=0;
    for(int i=1;i<=n;++i){
        for(int j=i;j<=n;++j){
            ans^=(a[i]+a[j]);
        }
    }
    cout<<ans<<'\n';
}

void Sort(int pos){
    vector<int> freq(2);
    for(int i=1;i<=n;++i){
        freq[(a[i]>>pos)&1]++;
    }
    freq[1]+=freq[0];
    for(int i=n;i>=1;--i){
        int id=(a[i]>>pos)&1;
        b[freq[id]]=a[i];
        freq[id]--;
    }
    for(int i=1;i<=n;++i){
        a[i]=b[i];
    }
}

int Check(int pos){
    int res=0;
    vector<vector<int64_t>> vec(2);
    for(int i=1;i<=n;++i){
        int64_t val=0;
        for(int j=0;j<pos;++j){
            if((a[i]>>j)&1){
                val|=1<<j;
            }
        }
        vec[(a[i]>>pos)&1].push_back(val);
    }
    assert(is_sorted(begin(vec[0]),end(vec[0])));
    assert(is_sorted(begin(vec[1]),end(vec[1])));
    int ptr=(int)vec[0].size()-1;
    for(int i=0;i<vec[0].size();++i){
        int64_t val=(1<<pos)-vec[0][i];
        while(ptr>=0&&vec[0][ptr]>=val){
            ptr--;
        }
        if(ptr+1<=i){
            res^=(i-(ptr+1)+1)%2;
        }
    }
    ptr=(int)vec[1].size()-1;
    for(int i=0;i<vec[1].size();++i){
        int64_t val=(1<<pos)-vec[1][i];
        while(ptr>=0&&vec[1][ptr]>=val){
            ptr--;
        }
        if(ptr+1<=i){
            res^=(i-(ptr+1)+1)%2;
        }
    }
    ptr=(int)vec[1].size()-1;
    for(int i=0;i<vec[0].size();++i){
        int64_t val=(1<<pos)-vec[0][i];
        while(ptr>=0&&vec[1][ptr]>=val){
            ptr--;
        }
        res^=(ptr+1)%2;
    }
    Sort(pos);
    return res;
}

void Sub2(){
    int64_t ans=0;
    for(int i=0;i<=31;++i){
        if(Check(i)){
            ans+=(int64_t)1<<i;
        }
    }
    cout<<ans;
}

void Gen(){
    srand(time(0));
    freopen("info1cup17_xorsum.inp","w",stdout);
    int n=rand()%5+1;
    cout<<n<<'\n';
    for(int i=1;i<=n;++i){
        cout<<rand()%10+1<<' ';
    }
    exit(0);
}

int main()
{
//    Gen();
//    freopen("info1cup17_xorsum.inp","r",stdin);
//    freopen("info1cup17_xorsum.out","w",stdout);
	ios_base::sync_with_stdio(0);
	cin.tie(0);
	cin>>n;
	for(int i=1;i<=n;++i){
        cin>>a[i];
	}
//	Sub1();
	Sub2();
    return 0;
}

Compilation message (stderr)

xorsum.cpp: In function 'int Check(int)':
xorsum.cpp:68:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for(int i=0;i<vec[0].size();++i){
                 ~^~~~~~~~~~~~~~
xorsum.cpp:78:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for(int i=0;i<vec[1].size();++i){
                 ~^~~~~~~~~~~~~~
xorsum.cpp:88:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for(int i=0;i<vec[0].size();++i){
                 ~^~~~~~~~~~~~~~
xorsum.cpp: In function 'void Gen()':
xorsum.cpp:111:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result]
     freopen("info1cup17_xorsum.inp","w",stdout);
     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

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