Leetcode - 3Sum With Multiplicity

https://leetcode.com/problems/3sum-with-multiplicity/

Given an integer array A, and an integer target, return the number of tuples i, j, k  such that i < j < k and A[i] + A[j] + A[k] == target.

As the answer can be very large, return it modulo 10^9 + 7.

Example 1:

Input: A = [1,1,2,2,3,3,4,4,5,5], target = 8
Output: 20
Explanation: 
Enumerating by the values (A[i], A[j], A[k]):
(1, 2, 5) occurs 8 times;
(1, 3, 4) occurs 8 times;
(2, 2, 4) occurs 2 times;
(2, 3, 3) occurs 2 times.

func threeSumMulti(A []int, target int) int {
    hash := map[int]int{}
    result := 0
    mod := 1000000007
    for i := 0; i < len(A); i++ {
        if v, ok := hash[target - A[i]]; ok {
            result = (result + v) % mod
        }
        for j := 0; j < i; j++ {
            tmp := A[i] + A[j]
            hash[tmp]++
        }
    }
    return result
}

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