2475. Number of Unequal Triplets in Array

Problem Link

Description

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You are given a 0-indexed array of positive integers nums. Find the number of triplets (i, j, k) that meet the following conditions:

• 0 <= i < j < k < nums.length
• nums[i], nums[j], and nums[k] are pairwise distinct.
  • In other words, nums[i] != nums[j], nums[i] != nums[k], and nums[j] != nums[k].

Return the number of triplets that meet the conditions.

 

Example 1:

Input: nums = [4,4,2,4,3]
Output: 3
Explanation: The following triplets meet the conditions:
- (0, 2, 4) because 4 != 2 != 3
- (1, 2, 4) because 4 != 2 != 3
- (2, 3, 4) because 2 != 4 != 3
Since there are 3 triplets, we return 3.
Note that (2, 0, 4) is not a valid triplet because 2 > 0.

Example 2:

Input: nums = [1,1,1,1,1]
Output: 0
Explanation: No triplets meet the conditions so we return 0.

 

Constraints:

• 3 <= nums.length <= 100
• 1 <= nums[i] <= 1000

Solution

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Python3

class Solution:
    def unequalTriplets(self, nums: List[int]) -> int:
        N = len(nums)
        res = 0
        
        for i in range(N):
            for j in range(i + 1, N):
                for k in range(j + 1, N):
                    if nums[i] != nums[j] and nums[i] != nums[k] and nums[j] != nums[k]:
                        res += 1
        
        return res