1608. Special Array With X Elements Greater Than or Equal X

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# 題目敘述

You are given an array nums of non-negative integers. nums is considered special if there exists a number x such that there are exactly x numbers in nums that are greater than or equal to x .

Notice that x does not have to be an element in nums .

Return x if the array is special, otherwise, return -1 . It can be proven that if nums is special, the value for x is unique.

# Example 1

Input: nums = [3,5]
Output: 2
Explanation: There are 2 values (3 and 5) that are greater than or equal to 2.

# Example 2

Input: nums = [0,0]
Output: -1
Explanation: No numbers fit the criteria for x.
If x = 0, there should be 0 numbers >= x, but there are 2.
If x = 1, there should be 1 number >= x, but there are 0.
If x = 2, there should be 2 numbers >= x, but there are 0.
x cannot be greater since there are only 2 numbers in nums.

# Example 3

Input: nums = [0,4,3,0,4]
Output: 3
Explanation: There are 3 values that are greater than or equal to 3.

# 解題思路

# Solution

class Solution {

    public int specialArray(int[] nums) {

        int n = nums.length;

        for (int x = 0; x <= n; x++) {

            int count = 0;

            for (int num : nums) {

                if (num >= x) {

                    count++;

                }

            }

            if (count == x) {

                return x;

            }

        }

        return -1;

    }

}