Count the duplicates in a list of tuples

Question

I have a list of tuples: a = [(1,2),(1,4),(1,2),(6,7),(2,9)] I want to check if one of the individual elements of each tuple matches the same position/element i

Answer 1

Maybe Dictionary can work better. Because in your code, you are traveling the list for twice. And this makes the complexity of your code O(n^2). And this is not a good thing :)

Best way is the travelling for once and to use 1 or 2 conditions for each traverse. Here is the my first solution for such kind of problem.

a = [(1,2),(1,4),(1,2),(6,7),(2,9)]

dict = {}
for (i,j) in a:
    if dict.has_key(i):
            dict[i] += 1
    else:
            dict[i] = 1

print dict

For this code, this will give the output:

{1: 3, 2: 1, 6: 1}

I hope it will be helpful.