Finding the missing list in Python-CodePudding

I have a list I arranged in order of increasing j. I want to find the missing j values. (To clarify, for [[8, 1]], i=8,j=1). The desired output is attached.

I=[[[8, 1]],
 [[1, 2]],
 [[0, 3]],
 [[15, 7]],
 [[7, 8]],
 [[2, 9], [8, 9]],
 [[9, 10]]]

The desired output is:

Missing=[4,5,6]

How can I produce the desired output?

CodePudding user response：

Generate a set of numbers that do appear in the list, and then identify the missing numbers by determining whether or not they appear in the set:

minimum = I[0][0][1]
maximum = I[-1][0][1]
included_numbers = {entry for sublist in I for _, entry in sublist}
[i for i in range(minimum, maximum) if i not in included_numbers]

This outputs:

[4, 5, 6]

CodePudding user response：

The easiest would be to use sets. One set with the expected j values and one with the actual values. Then you can subtract the sets and print the missing ones.

items = [[[8, 1]],
         [[1, 2]],
         [[0, 3]],
         [[15, 7]],
         [[7, 8]],
         [[2, 9], [8, 9]],
         [[9, 10]]]

expected = set(range(1, 11))
actual = set([item[0][1] for item in items])
print(expected - actual)

If you need the output as a list, simply cast to a list like so:

missing = list(expected - actual)

CodePudding user response：

Assuming the value starts at 1, the following code can solve the problem"

def find_missing(I):
  current_max = 1
  missing = []
  for row in I:
    for i,j in row:
      if j > current_max:
        missing.extend(list(range(current_max,j)))
      current_max = j 1
  return missing