algoadvance

We are given two arrays nums and index. We need to create a target array under the following conditions:

1. Initially, the target array is empty.
2. We process the nums array one element at a time along with the corresponding element in the index array.
3. For each element in nums, we insert it at the position specified in the corresponding element in index.

Finally, we need to return the target array.

Example:

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

Constraints:

• nums is an array with distinct integers.
• index has the same length as nums.
• The elements in index are valid indices of the target array when elements are inserted progressively.

Clarifying Questions

1. Can we assume that every element in index is within the valid range of the current target array’s length?
   • Yes, the problem guarantees this.
2. Is it required to handle any special input cases (like empty nums and index arrays)?
   • No, we assume the inputs are always valid as per the problem constraints.

Strategy

We can iterate over the elements of nums and index. For each element in nums, we use the corresponding index to determine where to insert the element in the target array. Python’s list insert method will be used for this purpose, as it handles the insertion of an element at a specified position directly.

Here is the step-by-step strategy:

1. Initialize an empty target array.
2. Iterate through the elements of nums and index together.
3. For each pair (num, idx), use the insert method to insert num at position idx in the target array.
4. Continue until all elements are processed.
5. Return the target array.

Code

def createTargetArray(nums, index):
    target = []
    for num, idx in zip(nums, index):
        target.insert(idx, num)
    return target

Time Complexity

The time complexity of the insert method in a list is O(n) in the worst case, because elements might need to be shifted to make room for the new element. Given this, if we are inserting n elements one by one, the overall time complexity will be:

• O(n^2) due to the repeated insertion operation.

This is acceptable within reason for smaller value ranges of nums and index, as typically posed in coding interview problems.

Example Execution

Let’s run through the provided example:

# Test the function with the given example
nums = [0, 1, 2, 3, 4]
index = [0, 1, 2, 2, 1]

print(createTargetArray(nums, index))  # Output should be [0, 4, 1, 3, 2]

This completes the problem-solving process for the given task.

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