Submission #1110775

#	Time	Username	Problem	Language	Result	Execution time	Memory
1110775		_callmelucian	XOR Sum (info1cup17_xorsum)	C++14	45 / 100	1639 ms	26776 KiB

xorsum

#include <bits/stdc++.h>
using namespace std;

typedef long long ll;
typedef long double ld;
typedef pair<ll,ll> pl;
typedef pair<int,int> pii;
typedef tuple<int,int,int> tpl;

#define all(a) a.begin(), a.end()
#define filter(a) a.erase(unique(all(a)), a.end())

int main()
{
    ios::sync_with_stdio(0);
    cin.tie(0);

    int n; cin >> n;
    vector<int> a(n), ord(n);

    for (int i = 0; i < n; i++) {
        cin >> a[i];
        ord[i] = i;
    }

    int ans = 0;
    for (int bit = 0; bit < 31; bit++) {
        // sort
        vector<int> zeroBit, oneBit, vec(n);
        for (int u : ord) {
            if ((a[u] >> bit) & 1) oneBit.push_back(u);
            else zeroBit.push_back(u);
        }
        ord = zeroBit, ord.insert(ord.end(), all(oneBit));

        // last (`bit` + 1) bits
        for (int i = 0; i < n; i++)
            vec[i] = a[ord[i]] & ((1 << (bit + 1)) - 1);

        // calculate
        for (int i = 0; i < ord.size(); i++) {
            int zero = -1, one = -1, two = -1;
            for (int step = i + 1; step >= 1; step /= 2) {
                while (zero + step <= i && ((vec[zero + step] + vec[i]) >> bit) <= 0) zero += step;
                while (one + step <= i && ((vec[one + step] + vec[i]) >> bit) <= 1) one += step;
                while (two + step <= i && ((vec[two + step] + vec[i]) >> bit) <= 2) two += step;
            }
            int cntOne = one - zero + i - two;
            if (cntOne & 1) ans ^= (1 << bit);
        }
    }
    cout << ans << "\n";

    return 0;
}

Compilation message (stderr)

xorsum.cpp: In function 'int main()':
xorsum.cpp:41:27: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   41 |         for (int i = 0; i < ord.size(); i++) {
      |                         ~~^~~~~~~~~~~~

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