217. Contains Duplicate

Problem

Given an integer array nums, return true if any value appears at least twice in the array, and return false if every element is distinct.

https://leetcode.com/problems/contains-duplicate/

Example 1:

Input: nums = [1,2,3,1]
Output: true
Explanation:
The element 1 occurs at the indices 0 and 3.

Example 2:

Input: nums = [1,2,3,4]
Output: false
Explanation:
All elements are distinct.

Example 3:

Input: nums = [1,1,1,3,3,4,3,2,4,2]
Output: true

Constraints:

1 <= nums.length <= 10⁵
-10⁹ <= nums[i] <= 10⁹

Test Cases

1 2	class Solution: def containsDuplicate(self, nums: List[int]) -> bool:

solution_test.py

import pytest

from solution import Solution


@pytest.mark.parametrize('nums, expected', [
    ([1,2,3,1], True),
    ([1,2,3,4], False),
    ([1,1,1,3,3,4,3,2,4,2], True),
])
class Test:
    def test_solution(self, nums, expected):
        sol = Solution()
        assert sol.containsDuplicate(nums) == expected

Thoughts

用集合检查数字是否已经见过。

Code

solution.py

class Solution:
    def containsDuplicate(self, nums: list[int]) -> bool:
        known = set()
        for v in nums:
            if v in known:
                return True
            known.add(v)

        return False

本文除了题目描述（Problem）部分之外，其他内容由 Calf 原创，采用 CC BY-NC-SA 4.0 许可协议，转载请注明出处。