Grokking Data Structures & Algorithms for Coding Interviews
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Problem 3: Unique Number of Occurrences (easy)
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Problem Statement

Given an array of integers, determine if the number of times each distinct integer appears in the array is unique.

In other words, the occurrences of each integer in the array should be distinct from the occurrences of every other integer.

Examples:

    • Input: [4, 5, 4, 6, 6, 6]
    • Expected Output: true
    • Justification: The number 4 appears 2 times, 5 appears 1 time, and 6 appears 3 times. All these occurrences (1, 2, 3) are unique.
    • Input: [7, 8, 8, 9, 9, 9, 10, 10]
    • Expected Output: false
    • Justification: The number 7 appears 1 time, 8 appears 2 times, 9 appears 3 times, and 10 appears 2 times. The occurrences are not unique since the number 2 appears twice.
    • Input: [11, 12, 13, 14, 14, 15, 15, 15]
    • Expected Output: false
    • Justification: The number 11 appears 1 time, 12 appears 1 time, 13 appears 1 time, 14 appears 2 times, and 15 appears 3 times. These occurrences are not unique.

Constraints:

  • 1 <= arr.length <= 1000
  • -1000 <= arr[i] <= 1000

Try it yourself

Try solving this question here:

Python3
Python3
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