permCheck.md

Description: Given an array of integers, check if it is a permutation of the first n positive integers (i.e., contains all numbers from 1 to n exactly once). Return 1 if it is a permutation, otherwise return 0.

Note: The array may contain duplicates or numbers outside the range 1 to n.

Examples

Example 1:

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

Example 2:

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

Example 3:

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

Example 4:

Input: nums = [1] Output: 1

Example 5:

Input: nums = [2, 1, 4, 3, 5] Output: 1

Algorithmic Steps This problem can be solved using a set or boolean array to track seen numbers:

1. Initialize a set or boolean array of size n.
2. Iterate through the array:
   • If the number is out of range or already seen, return 0.
   • Mark the number as seen.
3. If all numbers from 1 to n are seen exactly once, return 1.

Time and Space complexity:

• Time complexity: O(n), where n is the number of elements in the array.
• Space complexity: O(n).