Submission #499263

#	Time	Username	Problem	Language	Result	Execution time	Memory
499263		LucaIlie	XOR Sum (info1cup17_xorsum)	C++17	100 / 100	993 ms	21456 KiB

xorsum

#include <iostream>
#include <algorithm>
#include <math.h>

#define MAX_N 1000000

using namespace std;

int v[MAX_N], ant[MAX_N], rest[MAX_N];

int countLower( int v[], int n, int a ) {
    int st, dr, mij;

    st = 0;
    dr = n;
    while ( dr - st > 1 ) {
        mij = (st + dr) / 2;

        if ( v[mij] > a )
            dr = mij;
        else
            st = mij;
    }

    if ( v[st] > a )
        return 0;
    return st + 1;
}

int main() {
    int n, m, maxLog2, st, dr, leftR, rightR, res, i, j, p;
    long long nrSume;

    cin >> n;
    maxLog2 = 0;
    for ( i = 0; i < n; i++ ) {
        cin >> v[i];
        if ( log2( v[i] ) > maxLog2 )
            maxLog2 = log2( v[i] );
    }

    res = 0;
    for ( p = maxLog2 + 1;  p >= 0; p-- ) {
        if ( p <= maxLog2 ) {
            j = 0;
            while ( j < n && rest[j] < (1 << (p + 1)) )
                j++;
            m = j;

            i = 0;
            while ( i < m && j < n ) {
                if ( ant[i] < ant[j] - (1 << (p + 1))  ) {
                    rest[i + j - m] = ant[i];
                    i++;
                } else {
                    rest[i + j - m] = ant[j] - (1 << (p + 1));
                    j++;
                }
            }
            while ( i < m ) {
                rest[n - m + i] = ant[i];
                i++;
            }
            while ( j < n ) {
                rest[j] = ant[j] - (1 << (p + 1));
                j++;
            }
        } else {
            for ( i = 0; i < n; i++ )
                rest[i] = v[i] & ((1 << (p + 1)) - 1);
            sort( rest, rest + n );
        }

        nrSume = 0;
        st = dr = 0;
        for ( i = n - 1; i >= 0; i-- ) {
            leftR = (1 << p) - rest[i];
            if ( leftR < 0 )
                leftR += (1 << (p + 1));
            rightR = (1 << (p + 1)) - 1 - rest[i];
            if ( rightR < 0 )
                rightR += (1 << (p + 1));

            if ( rest[st] > leftR )
                st = 0;
            while ( st < n && rest[st] < leftR )
                st++;

            if ( rest[dr] > rightR )
                dr = 0;
            while ( dr < n && rest[dr] <= rightR )
                dr++;

            if ( leftR <= rightR ) {
                nrSume += dr - st;
                if ( leftR <= rest[i] && rest[i] <= rightR )
                    nrSume++;
            } else {
                nrSume += n - st + dr;
                if ( leftR <= rest[i] || rest[i] <= rightR )
                    nrSume++;
            }

            if ( st > 0 )
                st--;
            if ( dr > 0 )
                dr--;
        }
        nrSume /= 2;

        if ( nrSume % 2 == 1 )
            res += (1 << p);

        for ( i = 0; i < n; i++ )
            ant[i] = rest[i];
    }

    cout << res;

    return 0;
}

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