LeetCode [1313] Decompress Run-Length Encoded List

 1313. Decompress Run-Length Encoded List

Easy

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

1 2 3 4 5 6 7 8 9 10 11 12 13

class Solution { public int[] decompressRLElist(int[] nums) { List<Integer> ret = new ArrayList<>(); for(int i=0; i<nums.length; i += 2) { for(int j=0; j<nums[i]; ++j) { ret.add(nums[i+1]); } } return ret.stream().mapToInt(i->i).toArray(); } }