Submission #551104

#	Time	Username	Problem	Language	Result	Execution time	Memory
551104		Olympia	XOR Sum (info1cup17_xorsum)	C++17	7 / 100	1688 ms	8132 KiB

xorsum

#include <iostream>
#include <vector>
#include <iomanip>
#include <algorithm>
#include <cassert>
#include <map>
#include <complex>
#include <cmath>
#include <set>
#include <queue>
using namespace std;

#pragma GCC target ("avx2")
#pragma GCC optimization ("O3")
#pragma GCC optimization ("unroll-loops")
int res (vector<int>& a, int x) {
    //how many are <= x
    int r = a.size() - 1;
    int ans = 0;
    for (int i = 0; i < a.size(); i++) {
        if (a[i] + a[0] > x) {
            break;
        }
        while (a[r] + a[i] > x) {
            r--;
        }
        ans += abs(r) + 1 - (r >= i);
    }
    assert(ans % 2 == 0);
    ans /= 2;
    for (int i = 0; i < a.size(); i++) {
        ans += (2 * a[i] <= x);
    }
    return ans;
}
int res (vector<int>& a, int l, int r) {
    return res(a, r) - res(a, l - 1);
}
int main () {
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    int n; cin >> n;
    vector<int> v(n);
    for (int i = 0; i < n; i++)
        cin >> v[i];
    int ans = 0;
    for (int b = 0; b < 31; b++) {
        vector<int> a(n);
        for (int i = 0; i < a.size(); i++) {
            a[i] = v[i] & ((1 << (b + 1)) - 1);
        }
        sort(a.begin(), a.end());
        int r = 0;
        r += res(a, (1 << b), (1 << (b + 1)) - 1);
        r += res(a, (1 << b) + (1 << (b + 1)), (1 << (b + 2)) - 1);
        ans += (1 << b) * (r % 2);
    }
    cout << ans;
}

Compilation message (stderr)

xorsum.cpp:14: warning: ignoring '#pragma GCC optimization' [-Wunknown-pragmas]
   14 | #pragma GCC optimization ("O3")
      | 
xorsum.cpp:15: warning: ignoring '#pragma GCC optimization' [-Wunknown-pragmas]
   15 | #pragma GCC optimization ("unroll-loops")
      | 
xorsum.cpp: In function 'int res(std::vector<int>&, int)':
xorsum.cpp:20:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   20 |     for (int i = 0; i < a.size(); i++) {
      |                     ~~^~~~~~~~~~
xorsum.cpp:31:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   31 |     for (int i = 0; i < a.size(); i++) {
      |                     ~~^~~~~~~~~~
xorsum.cpp: In function 'int main()':
xorsum.cpp:49:27: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   49 |         for (int i = 0; i < a.size(); i++) {
      |                         ~~^~~~~~~~~~

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