Build Array from Permutation.

Problem in one line

Given a zero-based permutation nums, build ans where ans[i] = nums[nums[i]].

Approach

1. Create an output array result of the same length.
2. For each index i, set ans[i] to the element located at index nums[i] in nums.
3. Return result.

Complexity

• Time: O(n) — one loop through the array.
• Space: O(n) — for the output array (cannot be avoided if you must return a new array).

Code (Java)

class Solution {
    public int[] buildArray(int[] nums) {
        int n = nums.length;
        int[] result = new int[n];
        for (int i = 0; i < n; i++) {
            result[i] = nums[nums[i]];
        }
        return result;
    }
}