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46 lines
965 B
Python
46 lines
965 B
Python
"""
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1426. Counting Elements
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Difficulty: Easy
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https://leetcode.com/problems/counting-elements/
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──────────────────────────────────────────────────
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Given an integer array arr, count how many elements x there are, such
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that x + 1 is also in arr. If there are duplicates in arr, count them
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separately.
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Example 1:
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Input: arr = [1,2,3]
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Output: 2
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Explanation: 1 and 2 are counted cause 2 and 3 are in arr.
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Example 2:
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Input: arr = [1,1,3,3,5,5,7,7]
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Output: 0
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Explanation: No numbers are counted, cause there is no 2, 4, 6, or 8
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in arr.
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Constraints:
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• 1 <= arr.length <= 1000
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• 0 <= arr[i] <= 1000
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"""
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class Solution:
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def countElements(self, arr: List[int]) -> int:
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arr_set = set(arr)
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count = 0
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for n in arr:
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sum = n + 1
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if sum in arr_set:
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count += 1
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return count
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