1608. 特殊数组的特征值

输入：nums = [3,5]
输出：2
解释：有 2 个元素（3 和 5）大于或等于 2 。

func specialArray(nums []int) int {

    counting := make([]int, 1001)
    for i := range nums {
        counting[nums[i]]++
    }

    for i := len(counting)-2; i > -1; i-- {
        counting[i] += counting[i+1]
    }

    for i := 0; i <= len(nums); i++ {
        if counting[i] == i {
            return i
        }
    }
    
    return -1
}