Good Pairs

Unit 2 Session 2 (Click for link to problem statements)

U-nderstand

Understand what the interviewer is asking for by using test cases and questions about the problem.

• Q
  • A

P-lan

Plan the solution with appropriate visualizations and pseudocode.

General Idea: First, find out how many of each element are in the list. Then calculate how many possible pairs can exist for each value, and add these up.

1) First, create a frequency map for the list (

⚠️ Common Mistakes

I-mplement

def numIdenticalPairs(nums):
    # Frequency map to count occurrences of each number
    frequency_map = {}
    for num in nums:
        if num in frequency_map:
            frequency_map[num] += 1
        else:
            frequency_map[num] = 1
            
    # Count the number of good pairs
    good_pairs = 0
    for count in frequency_map.values():
        good_pairs += count * (count - 1) // 2  # Combination of 2 from n
        
    return good_pairs