README.md

1534. Count Good Triplets

Given an array of integers arr, and three integers a, b and c. You need to find the number of good triplets.

A triplet (arr[i], arr[j], arr[k]) is good if the following conditions are true:

• 0 <= i < j < k < arr.length
• |arr[i] - arr[j]| <= a
• |arr[j] - arr[k]| <= b
• |arr[i] - arr[k]| <= c

Where |x| denotes the absolute value of x.

Return the number of good triplets.

Example 1:

Input: arr = [3,0,1,1,9,7], a = 7, b = 2, c = 3
Output: 4
Explanation: There are 4 good triplets: [(3,0,1), (3,0,1), (3,1,1), (0,1,1)].

Example 2:

Input: arr = [1,1,2,2,3], a = 0, b = 0, c = 1
Output: 0
Explanation: No triplet satisfies all conditions.

Constraints:

• 3 <= arr.length <= 100
• 0 <= arr[i] <= 1000
• 0 <= a, b, c <= 1000

Solutions (Ruby)

1. Brute Force

# @param {Integer[]} arr
# @param {Integer} a
# @param {Integer} b
# @param {Integer} c
# @return {Integer}
def count_good_triplets(arr, a, b, c)
    ret = 0

    for i in 0...arr.length
        for j in (i + 1)...arr.length
            if (arr[i] - arr[j]).abs <= a
                for k in (j + 1)...arr.length
                    if (arr[j] - arr[k]).abs <= b and (arr[i] - arr[k]).abs <= c
                        ret += 1
                    end
                end
            end
        end
    end

    return ret
end