Positive id

1) change into a list of sets

x = [set(item.split(","))  for item in suspects]

max = 0
for i in range(len(x)):
    for j in range(i+1,len(x)):
         common = len(x[i]&x[j])  # intersection
         if common > max:
             max = common
return max


Mergesort 
How many recursive calls with a list of 8 when the
base case is len == 1. 

8 numbers  M(4) + M(4)
          M(2) M(2)  M(2) M(2)
        M(1) * 8

14 recursive calls

def mystery(num)
   if num > 10:
       return 1 + mystery(num-3)
   else:
       return 2

mystery(17)

mys(17) = 1 + M(14)   = 1 + 4 = 5
mys(14) = 1 + M(11)   = 1 + 3 = 4
mys(11) = 1 + M(8)   = 1 + 2 = 3
M(8) = 2

3 recursive calls