number_of_good_pairs.py

# Question:

# Given an array of integers nums, return the number of good pairs.

# A pair (i, j) is called good if nums[i] == nums[j] and i < j.

# 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

def numIdenticalPairs(nums):
    freq = {} #frequency of number
    good_pairs = 0 #number of good pairs
    
    for num in nums: #for a number in the array
        if num in freq: # check if the number is in the frequency
            good_pairs += freq[num]
            freq[num] += 1
        else:
            freq[num] = 1
    
    return good_pairs