## Leetcode - Number of Good Pairs Solution

Given an array of integers `nums`

.

A pair `(i,j)`

is called *good* if `nums[i]`

== `nums[j]`

and `i`

< `j`

.

Return the number of *good* pairs.

**Example 1:**

```
Input: nums = [1,2,3,1,1,3]
Output: 4
Explanation: There are 4 good pairs (0,3), (0,4), (3,4), (2,5) 0-indexed.
```

**Example 2:**

```
Input: nums = [1,1,1,1]
Output: 6
Explanation: Each pair in the array are good.
```

**Example 3:**

```
Input: nums = [1,2,3]
Output: 0
```

**Constraints:**

`1 <= nums.length <= 100`

`1 <= nums[i] <= 100`

## Solution in Python

```
from collections import Counter
class Solution:
def numIdenticalPairs(self, nums: List[int]) -> int:
return sum((n)*(n-1)//2 for n in Counter(nums).values())
```