C++

1class Solution {
2  public:
3    vector<int> decompressRLElist(vector<int>& nums) {
4      vector<int> result;
5      for(int i=0; i<nums.size(); i+=2) 
6      {
7        int freq = nums[i];
8        int val = nums[i+1];
9
10        for(int j=0; j<freq; ++j)
11        {
12          result.push_back(val);
13        }
14      }
15      return result;
16    }
17};

JavaScript

1var decompressRLElist = function(nums) {
2  let result = []
3
4  for (let i=0; i<nums.length; i+=2) {
5    let f = nums[i];
6    let v = nums[i+1];
7
8    for (let j=0; j<f; ++j) {
9      result.push(v);
10    }
11  }
12
13  return result;
14};

Ruby

1def decompress_rl_elist(nums)
2    result = []
3    
4    for i in (0...nums.size()).step(2) do
5        f = nums[i]
6        v = nums[i+1]
7        
8        1.upto(f) do
9            result << v 
10        end
11    end
12    
13    result
14end