Practice/Google/Leetcode 2475. Number of Unequal Triplets in Array

Leetcode 2475. Number of Unequal Triplets in Array

CodingMust

Problem

Given an array of integers, count how many triplets of indices (i, j, k) exist where i < j < k and the values at these three positions are all different from each other.

In other words, for indices i, j, k where i < j < k, you need nums[i] ≠ nums[j], nums[j] ≠ nums[k], and nums[i] ≠ nums[k].

Requirements

1. Return the total count of valid triplets
2. The indices must satisfy i < j < k
3. The three values at these indices must all be pairwise distinct
4. Consider only valid index triplets within the array bounds

Constraints

• 3 ≤ nums.length ≤ 100
• 1 ≤ nums[i] ≤ 1000
• Time complexity should be reasonable for the input size
• Space complexity: O(n) or better preferred

Examples

Example 1:

` Input: nums = [4, 4, 2, 4, 3] Output: 3 Explanation: The valid triplets are:

• (0, 2, 4): values [4, 2, 3] - all different
• (1, 2, 4): values [4, 2, 3] - all different
• (2, 3, 4): values [2, 4, 3] - all different `

Example 2:

Input: nums = [1, 1, 1, 1, 1] Output: 0 Explanation: All elements are identical, so no triplet can have three different values.

Example 3:

Input: nums = [1, 2, 3] Output: 1 Explanation: Only one triplet (0, 1, 2) with values [1, 2, 3], all distinct.