Let me try explaining an input. Here is Example 1:

Input:

nums = [1,2,3,1,1,3]

Output: 4

Explanation: There are 4 good pairs, here are the indices: (0,3), (0,4), (3,4), (2,5).

For example, how (0,3) is a good pair? To be a good pair, it should hold the ...

This approach works because we only want pairs (val1, val2) where val1 is smaller. Therefore when we encounter a new index that stores an integer, we know all the indexes we previously discovered for this integer must be smaller than our current index. Therefore the num...

i still didn't got the concept how the p-1 pairs are being added and it forms a good pair , this last line is bit confusing for me . although i did it with nested for loop , but that was O(n2) complexity , v poor . compared to this approach . can anyone explain the last...

If you are familiar with the common algorithm "Find The Frequency of Elements in Array" using HashTable. This problem is basically all about this. I strongly recommend understanding this algorithm first. Then Good Pairs will be easier.

By finding the frequency both con...