https://app.codility.com/demo/results/trainingRDQ5FR-JJ4/

fish.java

// you can also use imports, for example:
import java.util.*;

// you can write to stdout for debugging purposes, e.g.
// System.out.println("this is a debug message");

class Solution {
    public int solution(int[] A, int[] B) {
        ArrayList<Integer> up_sizes = new ArrayList<>();
        int lives = 0;
        
        for(int i=A.length-1; i>=0; i--) {
            if (B[i] == 0) {
                up_sizes.add(A[i]);
                continue;
            }
            
            for(int j=up_sizes.size()-1; j>=0; j--) {
                if (up_sizes.get(j) > A[i]) {
                    break;
                }
                
                up_sizes.remove(j);
            }
            
            if (up_sizes.size() == 0) {
                lives++;
            } 
        }
        
        lives += up_sizes.size();
        return lives;
    }
}