1313-DecompressRunLengthEncodedList.go

package main

// 1313. 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 [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

import "fmt"

func decompressRLElist(nums []int) []int {
    res := []int{}
    for i := 0; i <= len(nums) - 2; i += 2 {
        freq, num := nums[i], nums[i + 1]
        for j := freq; j > 0; j-- {
            res = append(res, num)
        } 
    }
    return res
}

func decompressRLElist1(nums []int) []int {
    res := make([]int, 0, 1)
    for i := 0; i < len(nums); i += 2 {
        for j := 1; j <= nums[i]; j++ {
            res = append(res, nums[i+1])
        }
    }
    return res
}

func main() {
    // 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].
    fmt.Println(decompressRLElist([]int{1,2,3,4})) // [2,4,4,4]
    // Example 2:
    // Input: nums = [1,1,2,3]
    // Output: [1,3,3]
    fmt.Println(decompressRLElist([]int{1,1,2,3})) // [1,3,3]

    fmt.Println(decompressRLElist1([]int{1,2,3,4})) // [2,4,4,4]
    fmt.Println(decompressRLElist1([]int{1,1,2,3})) // [1,3,3]
}