Practice/Meta/Leetcode 1313. Decompress Run-Length Encoded List

Leetcode 1313. Decompress Run-Length Encoded List

CodingOptional

Problem

You are given an array of integers where the elements come in consecutive pairs. Each pair represents compressed data in the format [frequency, value]. Your task is to decompress this data by expanding each pair into a sequence where the value appears exactly frequency times.

The pairs are processed in order from left to right, and all expanded sequences are concatenated together to form the final result.

Requirements

1. Process pairs sequentially from the beginning of the input array
2. For each pair [freq, val], add val to the output freq times
3. Return the fully expanded sequence as a single array
4. The input array will always have an even length (complete pairs)

Constraints

• 2 <= nums.length <= 100
• nums.length % 2 == 0 (always even)
• 1 <= nums[i] <= 100
• 1 <= frequency <= 50 for all frequency values
• The total length of the decompressed output will not exceed 1000 elements

Examples

Example 1:

Input: nums = [1, 2, 3, 4] Output: [2, 4, 4, 4] Explanation: The first pair [1, 2] means "one occurrence of 2", giving us [2]. The second pair [3, 4] means "three occurrences of 4", giving us [4, 4, 4]. Concatenating these gives [2, 4, 4, 4].

Example 2:

Input: nums = [1, 1] Output: [1] Explanation: One occurrence of the value 1.

Example 3:

` Input: nums = [4, 5, 2, 5, 3, 5] Output: [5, 5, 5, 5, 5, 5, 5, 5, 5] Explanation:

• First pair [4, 5]: four 5s
• Second pair [2, 5]: two 5s
• Third pair [3, 5]: three 5s Total: nine 5s `