Submission #518299

#	Time	Username	Problem	Language	Result	Execution time	Memory
518299		Be_dos	XOR Sum (info1cup17_xorsum)	C++17	77 / 100	1655 ms	13484 KiB

xorsum

#include <iostream>
#include <cmath>
#include <cctype>
#include <vector>
#include <algorithm>
#include <set>
#include <map>
#include <deque>
#include <stack>
#include <unordered_set>
#include <sstream>
#include <cstring>
#include <iomanip>
#include <queue>
#include <unordered_map>
#include <random>
#include <cfloat>
#include <chrono>
#include <bitset>
#include <complex>
#include <immintrin.h>
#include <cassert>

int32_t pairs_big_sum(int32_t* arr, int32_t n, int32_t target_sum) {
    int32_t right_num = 0;
    int64_t ans = 0;
    for(int32_t i = 0; i < n; i++) {
        if(arr[i] + arr[i] >= target_sum)
            ans++;
        while(right_num < n && arr[i] + arr[n - right_num - 1] >= target_sum)
            right_num++;
        ans += right_num;
    }
    return (ans / 2) % 2;
}

int32_t pairs_small_sum(int32_t* arr, int32_t n, int32_t* arr2, int32_t m, int32_t target_sum) {
    int32_t second_num = 0;
    while(second_num < m && arr[0] + arr2[second_num] <= target_sum)
        second_num++;
    int64_t ans = second_num;
    for(int32_t i = 1; i < n; i++) {
        while(second_num > 0 && arr[i] + arr2[second_num - 1] > target_sum)
            second_num--;
        ans += second_num;
    }
    return ans % 2;
}

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

    int32_t n;
    std::cin >> n;

    int32_t* arr = new int32_t[n];
    for(int32_t i = 0; i < n; i++)
        std::cin >> arr[i];

    /*int32_t ans2 = 0;
    for(int32_t i = 0; i < n; i++)
        for(int32_t j = i; j < n; j++)
            ans2 ^= arr[i] + arr[j];
    std::cout << ans2 << "\n";*/

    int32_t ans = 0;
    for(int32_t i = 29; i >= 0; i--) {
        std::sort(arr, arr + n);

        int32_t num_0 = 0;
        for(int32_t j = 0; j < n; j++)
            if((arr[j] & (1 << i)) == 0)
                num_0++;
        if(pairs_big_sum(arr, num_0, 1 << i) % 2 == 1)
            ans ^= 1 << i;
        for(int32_t j = num_0; j < n; j++)
            arr[j] &= INT32_MAX - (1 << i);
        if(pairs_big_sum(arr + num_0, n - num_0, 1 << i) % 2 == 1)
            ans ^= 1 << i;
        if(pairs_small_sum(arr, num_0, arr + num_0, n - num_0, (1 << i) - 1) % 2 == 1)
            ans ^= 1 << i;
    }

    std::cout << ans << "\n";
    return 0;
}
     

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