text: """
  https://leetcode.com/problems/decompress-run-length-encoded-list/
  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.
  
   
  
  Example 1:
  
  Input: nums = [1,2,3,4]
  Output: [2,4,4,4]
  Explanation: The first pair [1,2] means we have freq = 1 and val = 2 so we generate the array [2].
  The second pair [3,4] means we have freq = 3 and val = 4 so we generate [4,4,4].
  At the end the concatenation [2] + [4,4,4] is [2,4,4,4].
  Example 2:
  
  Input: nums = [1,1,2,3]
  Output: [1,3,3]
   
  
  Constraints:
  
  2 <= nums.length <= 100
  nums.length % 2 == 0
  1 <= nums[i] <= 100
  """
  
  # time complexity: O(n) but the one on the bottom is a little bit faster, space complexity: O(1)
  class Solution:
      def decompressRLElist(self, nums: List[int]) -> List[int]:
          """
          result = [0] * sum(nums[i] for i in range(0, len(nums), 2))
          pointer = 0
          for i in range(len(result)):
              if nums[pointer] == 0:
                  pointer += 2
              result[i] = nums[pointer+1]
              nums[pointer] -= 1
          return result
          """
          
          result = []
          for i in range(0, len(nums), 2):
              while nums[i] > 0:
                  result.append(nums[i+1])
                  nums[i] -= 1
          return result
  