LC1700. Number of Students Unable to Eat Lunch

from collections import deque
 
class Solution:
    def countStudents(self, students: List[int], sandwiches: List[int]) -> int:
        # More optimal to pop from right of lists
        sandwiches = sandwiches[::-1]
        # For optimal queue operations, we need a deque
        students = deque(students)
 
        # Constraint given in problem statement
        max_length = 100
 
        i = 0
        while sandwiches and i <= max_length:
            # Happy path!
            if students[0] == sandwiches[-1]:
                i = 0
                students.popleft()
                sandwiches.pop()
            # Else, send student to end of the queue and start
            # incrementing counter until we hit max_length
            else:
                students.append(students.popleft())
                i += 1
        
        return len(students)

Complexity

Time: $O(n)$
Space: $O(n)$ — depends I guess, but in this case, we had to make a deque data structure