# LeetCode 1313. Decompress Run-Length Encoded List

## Description

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 .
The second pair [3,4] means we have freq = 3 and val = 4 so we generate [4,4,4].
At the end the concatenation  + [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`

## Explanation

Step by 2 each time to add pairs.

## Python Solution

``````class Solution:
def decompressRLElist(self, nums: List[int]) -> List[int]:
results = []

for i in range(1, len(nums), 2):
freq = nums[i - 1]
value = nums[i]

for j in range(freq):
results.append(value)

return results``````
• Time Complexity: O(logN)
• Space Complexity: O(N)