1929-ConcatenationOfArray.go

package main

// 1929. Concatenation of Array
// Given an integer array nums of length n, 
// you want to create an array ans of length 2n where ans[i] == nums[i] and ans[i + n] == nums[i] for 0 <= i < n (0-indexed).

// Specifically, ans is the concatenation of two nums arrays.

// Return the array ans.

// Example 1:
// Input: nums = [1,2,1]
// Output: [1,2,1,1,2,1]
// Explanation: The array ans is formed as follows:
// - ans = [nums[0],nums[1],nums[2],nums[0],nums[1],nums[2]]
// - ans = [1,2,1,1,2,1]

// Example 2:
// Input: nums = [1,3,2,1]
// Output: [1,3,2,1,1,3,2,1]
// Explanation: The array ans is formed as follows:
// - ans = [nums[0],nums[1],nums[2],nums[3],nums[0],nums[1],nums[2],nums[3]]
// - ans = [1,3,2,1,1,3,2,1]

// Constraints:
//     n == nums.length
//     1 <= n <= 1000
//     1 <= nums[i] <= 1000

import "fmt"

func getConcatenation(nums []int) []int {
    return append(nums, nums...)
}

func getConcatenation1(nums []int) []int {
    n := len(nums)
    res := make([]int, 2 * n)
    for i, v := range nums{
        res[i], res[i + n] = v, v
    }
    return res
}

func main() {
    // Example 1:
    // Input: nums = [1,2,1]
    // Output: [1,2,1,1,2,1]
    // Explanation: The array ans is formed as follows:
    // - ans = [nums[0],nums[1],nums[2],nums[0],nums[1],nums[2]]
    // - ans = [1,2,1,1,2,1]
    fmt.Println(getConcatenation([]int{1,2,1})) // [1,2,1,1,2,1]
    // Example 2:
    // Input: nums = [1,3,2,1]
    // Output: [1,3,2,1,1,3,2,1]
    // Explanation: The array ans is formed as follows:
    // - ans = [nums[0],nums[1],nums[2],nums[3],nums[0],nums[1],nums[2],nums[3]]
    // - ans = [1,3,2,1,1,3,2,1]
    fmt.Println(getConcatenation([]int{1,3,2,1})) // [1,3,2,1,1,3,2,1]
    fmt.Println(getConcatenation([]int{1,2,3,4,5,6,7,8,9})) // [1,2,3,4,5,6,7,8,9,1,2,3,4,5,6,7,8,9]
    fmt.Println(getConcatenation([]int{9,8,7,6,5,4,3,2,1})) // [9,8,7,6,5,4,3,2,1,9,8,7,6,5,4,3,2,1]

    fmt.Println(getConcatenation1([]int{1,2,1})) // [1,2,1,1,2,1]
    fmt.Println(getConcatenation1([]int{1,3,2,1})) // [1,3,2,1,1,3,2,1]
    fmt.Println(getConcatenation1([]int{1,2,3,4,5,6,7,8,9})) // [1,2,3,4,5,6,7,8,9,1,2,3,4,5,6,7,8,9]
    fmt.Println(getConcatenation1([]int{9,8,7,6,5,4,3,2,1})) // [9,8,7,6,5,4,3,2,1,9,8,7,6,5,4,3,2,1]
}