1700. Number of Students Unable to Eat Lunch

problem

This can be solved without deque structure

Solution

#

• Since all elements in array are either 0 or 1 , So I use the arrayprefer(int[2]) to count how many students prefer each type of sandwich
• Using 0 as an example, while iterating through the sandwiches if the current sandwich is 0 but no student prefers it, then no one can take the sandwich. At that point, I return the number of remaining students who prefer the other type as the answer.

class Solution {
       public int countStudents(int[] students, int[] sandwiches) {
        int[] prefer = new int[2];

        for (int student : students) {
            prefer[student]++;
        }

        for (int sandwich : sandwiches) {
            if (prefer[sandwich] <= 0) return prefer[1 - sandwich];
            prefer[sandwich]--;
        }
        return 0;
    }
}