Tuple with Same Product

Given an array nums of distinct positive integers, return the number of tuples (a, b, c, d) such that a * b = c * d where a, b, c, and d are elements of nums, and a != b != c != d.

Example 1:

Input: nums = [2,3,4,6]
Output: 8
Explanation: There are 8 valid tuples:
(2,6,3,4) , (2,6,4,3) , (6,2,3,4) , (6,2,4,3)
(3,4,2,6) , (4,3,2,6) , (3,4,6,2) , (4,3,6,2)

Example 2:

Input: nums = [1,2,4,5,10]
Output: 16
Explanation: There are 16 valids tuples:
(1,10,2,5) , (1,10,5,2) , (10,1,2,5) , (10,1,5,2)
(2,5,1,10) , (2,5,10,1) , (5,2,1,10) , (5,2,10,1)
(2,10,4,5) , (2,10,5,4) , (10,2,4,5) , (10,2,4,5)
(4,5,2,10) , (4,5,10,2) , (5,4,2,10) , (5,4,10,2)

Example 3:

Input: nums = [2,3,4,6,8,12]
Output: 40

Example 4:

Input: nums = [2,3,5,7]
Output: 0

Constraints:

1 <= nums.length <= 1000
1 <= nums[i] <= 104
All elements in nums are distinct.

Solution:

because there is no duplicate in the numbers, every time we found two tuples whose product are the same, the tuples must be different

class Solution {
    public int tupleSameProduct(int[] nums) {
        Map<Integer, Integer> map = new HashMap();
        int res = 0;
        for (int i = 0; i < nums.length; i ++) {
            for (int j = i + 1; j < nums.length; j ++) {
                res += 8 * map.getOrDefault(nums[i] * nums[j], 0);
                map.put(nums[i] * nums[j], map.getOrDefault(nums[i] * nums[j], 0) + 1);
            }
        }
        return res;
    }
}