Special Array With X Elements Greater Than or Equal X.java

// Runtime: 1 ms (Top 88.84%) | Memory: 42.3 MB (Top 22.19%)
class Solution {
    public int specialArray(int[] nums) {
        int x = nums.length;
        int[] counts = new int[x+1];

        for(int elem : nums)
            if(elem >= x)
                counts[x]++;
            else
                counts[elem]++;

        int res = 0;
        for(int i = counts.length-1; i > 0; i--) {
            res += counts[i];
            if(res == i)
                return i;
        }

        return -1;
    }
}