笨笨的解决法

暴力方法，每个条件都用Collections.sort方法排序，判断最小的和最大的是否等于a和b

import java.util.*;
public class Main{
    public static void main(String[]args){
        Scanner input = new Scanner(System.in);
        while(input.hasNext()){
            String line1 = input.nextLine();
            String line2 = input.nextLine();
            int n = Integer.parseInt(line1.trim().split(" ")[0]);
            int m = Integer.parseInt(line1.trim().split(" ")[1]);
            int c = Integer.parseInt(line1.trim().split(" ")[2]);
            int d = Integer.parseInt(line1.trim().split(" ")[3]);
            int a = Math.min(c,d);
            int b = Math.max(c,d);
            int already[] = new int[m];
            int need[] = new int[2];
            need[0] = a;
            need[1] = b;
            for(int i=0;i<already.length;i++){
                already[i] = Integer.parseInt(line2.trim().split(" ")[i]);
            }
            int can = n-m;//还能做几个蛋糕
            ArrayList<Integer> list = new ArrayList<>();
            for (int i : already) {
                list.add(i);
            }
            //如果还能做两个以上
            if(can>=2){
                    list.add(a);
                    list.add(b);
                Collections.sort(list, new Comparator<Integer>() {
                    @Override
                    public int compare(Integer o1, Integer o2) {
                        return (o1).compareTo(o2);
                    }
                });
                if(a==list.get(0)&&b==list.get(list.size()-1)){
                    System.out.println("YES");
                }else{
                    System.out.println("NO");
                }

            }
            //只能做一个
            else if(can==1){
            //先把最小的加进去(a)
                list.add(a);
                Collections.sort(list, new Comparator<Integer>() {
                    @Override
                    public int compare(Integer o1, Integer o2) {
                        return (o1).compareTo(o2);
                    }
                });
                if(a==list.get(0)&&b==list.get(list.size()-1)){
                    System.out.println("YES");
                //如果加入最小的之后还不行
                }else{
                 //删除这一个（a）再加入b
                   list.remove(list.indexOf(a));
                   list.add(b);
                    Collections.sort(list, new Comparator<Integer>() {
                        @Override
                        public int compare(Integer o1, Integer o2) {
                            return (o1).compareTo(o2);
                        }
                    });
                    if(a==list.get(0)&&b==list.get(list.size()-1)){
                        System.out.println("YES");
                    }else{
                        System.out.println("NO");
                    }
                }
            // 不能做蛋糕了就只能从已经做的里面挑了。
            }else{
                Collections.sort(list, new Comparator<Integer>() {
                    @Override
                    public int compare(Integer o1, Integer o2) {
                        return (o1).compareTo(o2);
                    }
                });
                if(a==list.get(0)&&b==list.get(list.size()-1)){
                    System.out.println("YES");
                }else{
                    System.out.println("NO");
                }
            }
        }
    }
}