1577. Number of Ways Where Square of Number Is Equal to Product of Two Numbers

Given two arrays of integers nums1 and nums2, return the number of triplets formed (type 1 and type 2) under the following rules:

• Type 1: Triplet (i, j, k) if nums1[i]2 == nums2[j] * nums2[k] where 0 <= i < nums1.length and 0 <= j < k < nums2.length.
• Type 2: Triplet (i, j, k) if nums2[i]2 == nums1[j] * nums1[k] where 0 <= i < nums2.length and 0 <= j < k < nums1.length.

Example 1:

Input: nums1 = [7,4], nums2 = [5,2,8,9]
Output: 1
Explanation: Type 1: (1,1,2), nums1[1]^2 = nums2[1] * nums2[2]. (4^2 = 2 * 8).

Example 2:

Input: nums1 = [1,1], nums2 = [1,1,1]
Output: 9
Explanation: All Triplets are valid, because 1^2 = 1 * 1.
Type 1: (0,0,1), (0,0,2), (0,1,2), (1,0,1), (1,0,2), (1,1,2).  nums1[i]^2 = nums2[j] * nums2[k].
Type 2: (0,0,1), (1,0,1), (2,0,1). nums2[i]^2 = nums1[j] * nums1[k].

Example 3:

Input: nums1 = [7,7,8,3], nums2 = [1,2,9,7]
Output: 2
Explanation: There are 2 valid triplets.
Type 1: (3,0,2).  nums1[3]^2 = nums2[0] * nums2[2].
Type 2: (3,0,1).  nums2[3]^2 = nums1[0] * nums1[1].

Example 4:

Input: nums1 = [4,7,9,11,23], nums2 = [3,5,1024,12,18]
Output: 0
Explanation: There are no valid triplets.

Constraints:

• 1 <= nums1.length, nums2.length <= 1000
• 1 <= nums1[i], nums2[i] <= 10^5

# @lc code=start
using LeetCode

function num_triplets(nums1::Vector{Int}, nums2::Vector{Int})
    cnt1 = counter(nums1)
    cnt2 = counter(nums2)
    sqr_cnt1 = Dict(k ^ 2 => v for (k, v) in cnt1)
    sqr_cnt2 = Dict(k ^ 2 => v for (k, v) in cnt2)
    res = 0
    for (k1, v1) in cnt1
        for (k2, v2) in sqr_cnt2
            if k1 ^ 2 == k2
                res += (v1 - 1) * v1 * v2
            else
                res += cnt1[k2 ÷ k1] * v1 * v2
            end
        end
    end
    for (k1, v1) in cnt2
        for (k2, v2) in sqr_cnt1
            if k2 % k1 == 0
                if k1 ^ 2 == k2
                    res += (v1 - 1) * v1 * v2
                else
                    res += cnt2[k2 ÷ k1] * v1 * v2
                end
            end
        end
    end
    res ÷ 2
end
# @lc code=end

num_triplets (generic function with 1 method)

This page was generated using DemoCards.jl and Literate.jl.