# Equivalent Pairs

You are given a list of integers `nums`

. Return the number of pairs `i < j`

such that `nums[i] = nums[j]`

.

**Constraints**

`0 ≤ n ≤ 100,000`

where`n`

is the length of`nums`

https://binarysearch.com/problems/Equivalent-Pairs

## Examples

### Example 1

**Input**

- nums =
`[3, 2, 3, 2, 2]`

**Output**

- answer =
`4`

**Explanation**

We have index pairs `(0, 2)`

, `(1, 3)`

, `(1, 4)`

, `(3, 4)`

.

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