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
Solution:
using System;
using System.Collections.Generic;
using System.Text;
namespace LeetCode.AskGif.Easy.Array
{
public class DecompressRLElistSoln
{
public int[] DecompressRLElist(int[] nums)
{
var res = new List<int>();
for (int i = 0; i < nums.Length-1; i+=2)
{
for (int j = 0; j < nums[i]; j++)
{
res.Add(nums[i + 1]);
}
}
return res.ToArray();
}
}
}
Time Complexity: O(n)
Space Complexity: O(n) To store results.
Unit Tests:
using LeetCode.AskGif.Easy.Array;
using Microsoft.VisualStudio.TestTools.UnitTesting;
using System;
using System.Collections.Generic;
using System.Text;
namespace CodingUnitTest.Easy.Array
{
[TestClass]
public class DecompressRLElistSolnTests
{
[TestMethod]
public void DecompressRLElistSoln_First()
{
var arr = new int[] { 1, 2, 3, 4 };
var output = new int[] { 2, 4, 4, 4 };
var res = new DecompressRLElistSoln().DecompressRLElist(arr);
AreEqual(res, output);
}
[TestMethod]
public void DecompressRLElistSoln_Second()
{
var arr = new int[] { 1, 1, 2, 3 };
var output = new int[] { 1, 3, 3 };
var res = new DecompressRLElistSoln().DecompressRLElist(arr);
AreEqual(res, output);
}
private void AreEqual(int[] res, int[] output)
{
Assert.AreEqual(res.Length, output.Length);
for (int i = 0; i < res.Length; i++)
{
Assert.AreEqual(res[i], output[i]);
}
}
}
}
