Given an array of integers?arr, return?true?if the number of occurrences of each value in the array is?unique, or?false?otherwise.

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Example 1:

Input: arr = [1,2,2,1,1,3]Output: trueExplanation:?The value 1 has 3 occurrences, 2 has 2 and 3 has 1. No two values have the same number of occurrences.

Example 2:

Input: arr = [1,2]Output: false

Example 3:

Input: arr = [-3,0,1,-3,1,1,1,-3,10,0]Output: true

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Constraints:

• 1 <= arr.length?<= 1000

• -1000 <= arr[i] <= 1000

Runtime:?2 ms, faster than?82.86%?of?Java?online submissions for?Unique Number of Occurrences.

Memory Usage:?42.8 MB, less than?7.88%?of?Java?online submissions for?Unique Number of Occurrences.

map遍歷一遍，然后對value的大小判斷大于1就false；