3379. Transformed Array

3379. Transformed Array

Difficulty: Easy

Topics: Mid Level, Array, Simulation, Weekly Contest 427

You are given an integer array nums that represents a circular array. Your task is to create a new array result of the same size, following these rules:
For each index i (where 0 <= i < nums.length), perform the following independent actions:

• If nums[i] > 0: Start at index i and move nums[i] steps to the right in the circular array. Set result[i] to the value of the index where you land.
• If nums[i] < 0: Start at index i and move abs(nums[i]) steps to the left in the circular array. Set result[i] to the value of the index where you land.
• If nums[i] == 0: Set result[i] to nums[i].

Return the new array result.

Note: Since nums is circular, moving past the last element wraps around to the beginning, and moving before the first element wraps back to the end.

Example 1:

• Input: nums = [3,-2,1,1]
• Output: [1,1,1,3]
• Explanation:
  • For nums[0] that is equal to 3, If we move 3 steps to right, we reach nums[3]. So result[0] should be 1.
  • For nums[1] that is equal to -2, If we move 2 steps to left, we reach nums[3]. So result[1] should be 1.
  • For nums[2] that is equal to 1, If we move 1 step to right, we reach nums[3]. So result[2] should be 1.
  • For nums[3] that is equal to 1, If we move 1 step to right, we reach nums[0]. So result[3] should be 3.

Example 2:

• Input: nums = [-1,4,-1]
• Output: [-1,-1,4]
• Explanation:
  • For nums[0] that is equal to -1, If we move 1 step to left, we reach nums[2]. So result[0] should be -1.
  • For nums[1] that is equal to 4, If we move 4 steps to right, we reach nums[2]. So result[1] should be -1.
  • For nums[2] that is equal to -1, If we move 1 step to left, we reach nums[1]. So result[2] should be 4.

Constraints:

• 1 <= nums.length <= 100
• -100 <= nums[i] <= 100

Hint:

1. Simulate the operations as described in the statement

Solution:

We need to simulate the movement through a circular array and create a transformed result. Here’s the plan:

Approach:

For each element in the input array:

• If positive: move right nums[i] steps (wrapping around using modulo)
• If negative: move left abs(nums[i]) steps (wrapping around using modulo)
• If zero: keep zero

The key is handling the circular nature with proper modulo arithmetic, especially for negative movements.

Let's implement this solution in PHP: 3379. Transformed Array

<?php
/**
 * @param Integer[] $nums
 * @return Integer[]
 */
function constructTransformedArray(array $nums): array
{
    ...
    ...
    ...
    /**
     * go to ./solution.php
     */
}

// Test cases
echo constructTransformedArray([3, -2, 1, 1]) . "\n";           // Output: [1,1,1,3]
echo constructTransformedArray([-1, 4, -1]) . "\n";             // Output: [-1,-1,4]
?>

Explanation:

1. Array Length: Store the length of the array for modulo operations
2. Result Array: Initialize an array of the same size
3. Iterate: Process each element individually
4. Zero Case: If element is 0, set result to 0
5. Positive Case: Move right using modulo to handle wrap-around
6. Negative Case: Move left, ensuring the index stays positive by adding array length if negative

Complexity

• Time Complexity: O(n) where n is the length of the array
• Space Complexity: O(n) for the result array

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