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  1. Count Triplets
  2. Discussions

Count Triplets

  • sunny_jyrm
     + 0 comments

    Cleanest python solution:

    from collections import defaultdict
def countTriplets(nums, r):
    
    lefts = defaultdict(int)
    pairs = defaultdict(int)
    
    res = 0
    for n in nums:
        res += pairs[n]
                
        pairs[n*r] += lefts[n]
        
        lefts[n*r] += 1
        
    return res

    Can be made more succint using a key transform and one dictionary:

    from collections import defaultdict
def countTriplets(nums, r):
    lefts, res = defaultdict(int),0
    
    for n in nums:
        res += lefts[-n]
        lefts[-n*r] += lefts[n]
        lefts[n*r] += 1
        
    return res