Beautiful Arrangement II.cpp

class Solution {
public:
    vector<int> constructArray(int n, int k) {
        if(n < k + 1)return {};
        vector<int> res(n, 0);
        int i = 1, j = k + 1;
        while(i < j)
        {
            res[k + 1 - (j - i + 1)] = i;
            ++i;
            res[k + 1 - (j - i + 1)] = j;
            --j;
        }
        if(i == j)
            res[k] = i;
        for(int i = k + 1; i < n; ++i)
            res[i] = i + 1;
        return res;
    }
};