1import java.util.Arrays;
2
3public class SpecialArray {
4    public int specialArray(int[] nums) {
5        Arrays.sort(nums);
6        int n = nums.length;
7        for (int x = 0; x <= n; x++) {
8            int count = 0;
9            for (int num : nums) {
10                if (num >= x) {
11                    count++;
12                }
13            }
14            if (count == x) {
15                return x;
16            }
17        }
18        return -1;
19    }
20    public static void main(String[] args) {
21        SpecialArray sa = new SpecialArray();
22        int[] nums = {0, 4, 3, 0, 4};
23        System.out.println(sa.specialArray(nums));
24    }
25}

1using System.Linq;

class SpecialArray {
    private int CountGreaterEqual(int[] nums, int target) {
        return nums.Count(num => num >= target);
    }

    public int SpecialArrayFunc(int[] nums) {
        Array.Sort(nums);
        int left = 0, right = nums.Length;
        while (left <= right) {
            int mid = left + (right - left) / 2;
            int count = CountGreaterEqual(nums, mid);
            if (count == mid) {
                return mid;
            } else if (count < mid) {
                right = mid - 1;
            } else {
                left = mid + 1;
            }
        }
        return -1;
    }

    static void Main() {
        SpecialArray sa = new SpecialArray();
        int[] nums = {0, 4, 3, 0, 4};
        Console.WriteLine(sa.SpecialArrayFunc(nums));
    }
}