This is the 17th day of my participation in Gwen Challenge

describe

The school cafeteria offers circular and square sandwiches at lunch break, referred to by numbers 0 and 1 respectively. All students stand in a queue. Each student either prefers square or circular sandwiches.

The number of sandwiches in the cafeteria is equal to the number of students. The sandwiches are placed in a stack. At each step:

  • If the student at the front of the queue prefers the sandwich on the top of the stack, they will take it and leave the queue.
  • Otherwise, they will leave it and go to the queue’s end.

This continues until none of the queue students want to take the top sandwich and are thus unable to eat.

You are given two integer arrays students and sandwiches where sandwiches[i] is the type of the i​​​​​​th sandwich in the stack (i = 0 is the top of the stack) and students[j] is the preference of the j​​​​​​th student in the initial queue (j = 0 is the front of the queue). Return the number of students that are unable to eat.

Example 1:

Input: students = [1,1,0,0], sandwiches = [0,1,0,1] Output: 0 Explanation: - Front student leaves the top sandwich and returns to the end of the line making students = [1,0,0,1] Leaves the top sandwich and returns to the end of the line making students = [0,0,1,1]. - Front student takes the top Sandwiches and leaves the line making students = [0,1,1] and sandwiches = [1,0,1]. -front student leaves the top sandwich And returns to the end of the line making students = [1,1,0]. - Front student takes the top sandwich and leaves the Line making students = [1,0] and sandwiches = [0,1]. -front student leaves the top sandwich and returns to the end of The line making students = [0,1]. -front student takes the top sandwich and leaves the line making students = [1] sandwiches = [1]. - Front student takes the top sandwich and leaves the line making students = [] and sandwiches = []. Hence all students are able to eat.Copy the code

Example 2:

Input: students = [1,1,1,0,0,1], sandwiches = [1,0,0, 1,1] Output: 3Copy the code

Example 3:

1 <= students.length, sandwiches.length <= 100
students.length == sandwiches.length
sandwiches[i] is 0 or 1.
students[i] is 0 or 1.
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Note:

1 <= students.length, sandwiches.length <= 100
students.length == sandwiches.length
sandwiches[i] is 0 or 1.
students[i] is 0 or 1.
Copy the code

parsing

According to the question, is there are two kinds of sandwich 0 and 1, there is a row and sandwiches the same number of students waiting in line, they like to one of two kinds of sandwich, when a student turn, presence just like sandwich type, directly took leave, or go to a party the end of the line, when all the sandwich when nobody wants to end, Count the last few picky eaters left without a meal. The problem is long but not hard, just loop through the students with the while statement, if the ideal situation, the students and sandwiches all pop(0), otherwise the current students will only be placed at the end of the students, If the number of students who did not get the food is equal to the current number of students, the loop is broken, and the final number of students is the result.

answer

class Solution(object):
    def countStudents(self, students, sandwiches):
        """
        :type students: List[int]
        :type sandwiches: List[int]
        :rtype: int
        """
        count = 0
        while students:
            student = students.pop(0)
            if student == sandwiches[0]:
                count=0
                sandwiches.pop(0)
            else:
                count+=1
                students.append(student)
            if count==len(students):
                break
        return len(students)         	      
		
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The results

Runtime: 24 ms, faster than 70.16% of Python online submissions for Number of Students Unable to Eat Lunch. Memory Usage: The submissions in the Python online submissions list for Number of Students Unable to Eat Lunch.Copy the code

Original link: leetcode.com/problems/nu…

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