Largest Unique Number Python Solution

Tested Python solution for LeetCode 1133 with 20 pytest cases. Generate a practice environment with lcpy.

LeetCode 1133, Easy. Topics: Array, Hash Table, Sorting. View on LeetCode.

Generate this problem as a practice environment: tested reference solution, 20 parametrized pytest cases, and a playground notebook:

lcpy gen -n 1133   # by problem number
lcpy gen -s largest_unique_number   # by problem name

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Problem

Given an integer array nums, return the largest integer that only occurs once. If no integer occurs once, return -1.

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Examples

Input: nums = [5,7,3,9,4,9,8,3,1]
Output: 8

Explanation: The maximum integer in the array is 9 but it is repeated. The number 8 occurs only once, so it is the answer.

Input: nums = [9,9,8,8]
Output: -1

Explanation: There is no number that occurs only once.

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Constraints

• 1 <= nums.length <= 2000
• 0 <= nums[i] <= 1000

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Solution

Reference implementation from solution.py on GitHub, full suite in test_solution.py:

from collections import Counter


class Solution:
    # Time: O(n)
    # Space: O(n)
    def largest_unique_number(self, nums: list[int]) -> int:
        counts = Counter(nums)
        candidates = [value for value, count in counts.items() if count == 1]
        return max(candidates) if candidates else -1

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Complexity

Time	Space
O(n)	O(n)

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Tags

NeetCode All.