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.
Example 4:
Input: nums = [3,6,7,7,0] Output: -1
Constraints:
1 <= nums.length <= 100
0 <= nums[i] <= 1000
class Solution { public int specialArray(int[] nums) { int n = nums.length; int[] arr = new int[1001]; for(int i : nums) arr[i]++; for(int i = 0; i <= 100; i++) { if(n == i) return i; n -= arr[i]; } return -1; } }
牛逼了我的哥,先用constraint把各个数的频率count一下,然后因为一共不超过100个数,所以实际上nums【i】大于100的时候已经没用了,题目要求的是恰好有x个数大于等于x。
然后从0到100循环,如果剩余数n == i,说明n和i就是x,返回。否则由于这个数不是答案,所以n减去这个数的频率,比如【0,0,3,4,3】,到0的时候不符合,n-2=3,然后到了3直接3 == 3 返回。