1389. Create Target Array in the Given Order

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.

Python Code
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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

Java Code
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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;
    }
}

C++ Code
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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;
    }
};

Go Code
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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
}

TypeScript Code
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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;
}