Contiguous Array Python Solution with Tests

Tested Python solution for LeetCode 525 with 17 pytest cases. Generate a practice environment with lcpy.

LeetCode 525, Medium. Topics: Array, Hash Table, Prefix Sum. View on LeetCode.

Generate this problem as a practice environment: tested reference solution, 17 parametrized pytest cases, and a playground notebook:

lcpy gen -n 525   # by problem number
lcpy gen -s contiguous_array   # by problem name

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Problem

Given a binary array nums, return the maximum length of a contiguous subarray with an equal number of 0 and 1.

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Examples

Input: nums = [0,1]
Output: 2
Explanation: [0, 1] is the longest contiguous subarray with an equal number of 0 and 1.

Input: nums = [0,1,0]
Output: 2
Explanation: [0, 1] (or [1, 0]) is a longest contiguous subarray with equal number of 0 and 1.

Input: nums = [0,1,1,1,1,1,0,0,0]
Output: 6
Explanation: [1,1,1,0,0,0] is the longest contiguous subarray with equal number of 0 and 1.

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Constraints

• 1 <= nums.length <= 10^5
• nums[i] is either 0 or 1.

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Solution

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

class Solution:
    # Time: O(n)
    # Space: O(n)
    def find_max_length(self, nums: list[int]) -> int:
        count_map = {0: -1}
        count = 0
        max_len = 0

        for i, num in enumerate(nums):
            count += 1 if num == 1 else -1

            if count in count_map:
                max_len = max(max_len, i - count_map[count])
            else:
                count_map[count] = i

        return max_len

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Complexity

Time	Space
O(n)	O(n)

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Tags

Grind, NeetCode All.