void OddEvenSort(vector<int>& arr) {

for (int i = 0; i < arr.size(); ++i)

for (int j = ((i % 2 == 0) ? 0 : 1); j + 1 < arr.size(); j += 2)

if (arr[j] > arr[j + 1])

swap(arr[j], arr[j + 1]);

}