算法集 找出缺失的数字

题目描述：

找出1~n的数字中缺失的两个数

代码：

public class FindMissNumber {

    public static int[] findMissNumber(int[] arr) {
        if (null == arr || arr.length <= 1) {
            return new int[]{-1, -1};
        }
        boolean[] b = new boolean[arr.length + 2];

        int[] rets = new int[2];
        for (int i = 0; i < arr.length; i++) {
            b[arr[i] - 1] = true;
        }

        int j = 0;
        for (int i = 0; i < b.length; i++) {
            if (!b[i]) {
                rets[j++] = i + 1;
            }
        }

        return rets;
    }

    public static void main(String[] args) {
        int[] arr = {2, 4, 3, 9, 5, 6, 1};
        int[] missNumber = findMissNumber(arr);
        for (int i = 0; i < missNumber.length; i++) {
            System.out.println(missNumber[i]);
        }
    }

}