Most frequently asked interview question #10 with solution

We are given a list nums of integers representing a list compressed with run-length encoding.
Consider each adjacent pair of elements [freq, val] = [nums[2*i], nums[2*i+1]] (with i >= 0).  For each such pair, there are freq elements with value val concatenated in a sublist. Concatenate all the sublists from left to right to generate the decompressed list.
Return the decompressed list.

Input: nums = [1,2,3,4]
Output: [2,4,4,4]

Solution in C++:

 
    vector<int> decompressRLElist(vector<int>& nums) {
            vector<int> ret;
        for(int iter = 0; iter < nums.size();){
                int i = 0;
            while(i < nums.at(iter)){
                ++i;
                ret.push_back(nums.at(iter + 1));
            }
            iter += 2;
        }
        return ret;
    }