判断某个出栈顺序是否合法

public class PopSequence {

	public static boolean isQualified(int[] a, int[] b) {
		assert (true);
		HashSet<Integer> set = new HashSet<Integer>();
		for (int i=0; i<b.length-1; i++) {
			set.add(b[i]);
			if (b[i + 1] < b[i]) {
				for(int j=b[i]-1; j>b[i+1]; j--){
					if (!set.contains(j)){
						return false;
					}
				}
			}
		}
		return true;
	}

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		int[] a = { 1, 2, 3, 4, 5 };
		ArrayList<int[]> list = AllSequence.getAllSequence(a);
		int count = 0;
		for (int[] o : list) {
			boolean result = PopSequence.isQualified(a, o);
			if (result) {
				Tools.printArray(o);
				count++;
			}
		}
		System.out.println(count);
		
		boolean res = PopSequence.isQualified(a, new int[]{4,5,2,3,1});
		System.out.println(res);
	}

}