78 lines
1.6 KiB
C++
78 lines
1.6 KiB
C++
#include <iostream>
|
|
#include <cstdlib>
|
|
#include <ctime>
|
|
|
|
long long CalculateMaxSquare(long long* a, int size);
|
|
int Partition(long long* arr, int start, int end);
|
|
void QuickSort(long long* arr, int start, int end);
|
|
|
|
int Partition(long long* arr, int start, int end) {
|
|
long long pivot = arr[std::rand() % (end - start + 1) + start];
|
|
int i = start - 1;
|
|
int j = end + 1;
|
|
|
|
while (true) {
|
|
do {
|
|
++i;
|
|
} while (arr[i] > pivot);
|
|
|
|
do {
|
|
--j;
|
|
} while (arr[j] < pivot);
|
|
|
|
if (i >= j)
|
|
return j;
|
|
|
|
std::swap(arr[i], arr[j]);
|
|
}
|
|
}
|
|
|
|
void QuickSort(long long* arr, int start, int end) { // NOLINT(*-no-recursion)
|
|
if (start >= end)
|
|
return;
|
|
|
|
int pivot_idx = Partition(arr, start, end);
|
|
|
|
QuickSort(arr, start, pivot_idx);
|
|
QuickSort(arr, pivot_idx + 1, end);
|
|
}
|
|
|
|
long long CalculateMaxSquare(long long* arr, int size) {
|
|
long long sq_sum = 0;
|
|
|
|
long long* viable_numbers = new long long[size];
|
|
int viable_size = 0;
|
|
for (int i = 0; i < size - 1; ++i) {
|
|
if (std::abs(arr[i] - arr[i+1]) <= 1) {
|
|
viable_numbers[viable_size] = std::min(arr[i], arr[i+1]);
|
|
++i;
|
|
++viable_size;
|
|
}
|
|
}
|
|
|
|
QuickSort(viable_numbers, 0, viable_size - 1);
|
|
|
|
for (int i = 0; i < size - 1; i += 2) {
|
|
sq_sum += viable_numbers[i] * viable_numbers[i+1];
|
|
}
|
|
|
|
return sq_sum;
|
|
}
|
|
|
|
int main() {
|
|
int size;
|
|
std::cin >> size;
|
|
long long* a = new long long[size];
|
|
|
|
for (int i = 0; i < size; ++i) {
|
|
std::cin >> a[i];
|
|
}
|
|
|
|
std::srand(std::time(nullptr)); // stinky code, but i'm too lazy
|
|
QuickSort(a, 0, size - 1);
|
|
|
|
std::cout << CalculateMaxSquare(a, size);
|
|
|
|
delete[] a;
|
|
return 0;
|
|
}
|