使Python代码更快

Question

Is it possible to make this code run faster?

a,b=map(int,input().split())
c=list(map(int,input().split()))
d=list(map(int,input().split()))
e=list(map(int,input().split()))

happy=0

for i in c:
    if i in d:
        happy=happy+1
    elif i in e:
        happy=happy-1

print(happy)

The code has to increment or decrement happy variable depending on if elements of c list are present in d or e lists. This code runs fine for small number of elements in c , d and e lists. But when there are many elements , the code execution is terminated due to timeout.

What can I do to make it run faster?

Answer 1

You can avoid the loop. The variable happy is essentially the difference between the number of elements found in d and the number of elements found in e .

Could there be duplicates in c ?

If you want to count the same element only once, then you can use set , that implicitly remove duplicates:

set_c = set(c)
happy_match = set_c.intersect(d)
unhappy_match = set_c.intersect(e)

happy = len(happy) - len(unhappy_match)

If you want to count each occurrence (including duplicates), then you can apply the same logic to lists:

happy_match = sum(1 if el in d else 0 for el in c)
unhappy_match = sum(1 if el in e else 0 for el in c)

happy = len(happy) - len(unhappy_match)