Question

1389. Create Target Array in the Given Order

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Description

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

Solutions

Solution 1: Simulation

We create a list $target$ to store the target array. Since the problem guarantees that the insertion position always exists, we can directly insert in the given order into the corresponding position.

The time complexity is $O(n^2)$, and the space complexity is $O(n)$. Where $n$ is the length of the array.

class Solution:
  def createTargetArray(self, nums: List[int], index: List[int]) -> List[int]:
    target = []
    for x, i in zip(nums, index):
      target.insert(i, x)
    return target

class Solution {
  public int[] createTargetArray(int[] nums, int[] index) {
    int n = nums.length;
    List<Integer> target = new ArrayList<>();
    for (int i = 0; i < n; ++i) {
      target.add(index[i], nums[i]);
    }
    // return target.stream().mapToInt(i -> i).toArray();
    int[] ans = new int[n];
    for (int i = 0; i < n; ++i) {
      ans[i] = target.get(i);
    }
    return ans;
  }
}

class Solution {
public:
  vector<int> createTargetArray(vector<int>& nums, vector<int>& index) {
    vector<int> target;
    for (int i = 0; i < nums.size(); ++i) {
      target.insert(target.begin() + index[i], nums[i]);
    }
    return target;
  }
};

func createTargetArray(nums []int, index []int) []int {
  target := make([]int, len(nums))
  for i, x := range nums {
    copy(target[index[i]+1:], target[index[i]:])
    target[index[i]] = x
  }
  return target
}

function createTargetArray(nums: number[], index: number[]): number[] {
  const ans: number[] = [];
  for (let i = 0; i < nums.length; i++) {
    ans.splice(index[i], 0, nums[i]);
  }
  return ans;
}