createTargetArrayInTheGivenOrder.js

// LeetCode #1389. Create Target Array in the Given Order
/* Instructions
Given two arrays of integers nums and index. Your task is to create target array under the following rules:

    Initially target array is empty.
    From left to right read nums[i] and index[i], insert at index index[i] the value nums[i] in target array.
    Repeat the previous step until there are no elements to read in nums and index.

Return the target array.

It is guaranteed that the insertion operations will be valid.

 

Example 1:

Input: nums = [0,1,2,3,4], index = [0,1,2,2,1]
Output: [0,4,1,3,2]
Explanation:
nums       index     target
0            0        [0]
1            1        [0,1]
2            2        [0,1,2]
3            2        [0,1,3,2]
4            1        [0,4,1,3,2]

Example 2:

Input: nums = [1,2,3,4,0], index = [0,1,2,3,0]
Output: [0,1,2,3,4]
Explanation:
nums       index     target
1            0        [1]
2            1        [1,2]
3            2        [1,2,3]
4            3        [1,2,3,4]
0            0        [0,1,2,3,4]

Example 3:

Input: nums = [1], index = [0]
Output: [1]

 

Constraints:

    1 <= nums.length, index.length <= 100
    nums.length == index.length
    0 <= nums[i] <= 100
    0 <= index[i] <= i

*/

// Solution
const createTargetArray = function (nums, index) {
    // instantiate empty array, target
    let target = []

    // loop through nums
    for (let i = 0; i < nums.length; i++) {
        // check if element at index already exists, if it does...
        // add the element at nums index in that position and shift the other elements to the right
        if (target[index[i]] !== undefined) {
            target.splice(index[i], 0, nums[i])
        } else {
            // otherwise, set that index equal to the element at nums index
            target[index[i]] = nums[i]
        }
    }

    // return the filled out target array
    return target
}