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

Companies:
Amazon, Google

Related Topics:
Array

Similar Questions:

• String Compression (Medium)

Solution 1.

// OJ: https://leetcode.com/problems/decompress-run-length-encoded-list/
// Author: github.com/lzl124631x
// Time: O(N) where N is the length of the output array.
// Space: O(1)
class Solution {
public:
    vector<int> decompressRLElist(vector<int>& nums) {
        vector<int> ans;
        for (int i = 0; i < nums.size(); i += 2) {
            for (int j = 0; j < nums[i]; ++j) ans.push_back(nums[i + 1]);
        }
        return ans;
    }
};