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56 lines
1.2 KiB
Python
56 lines
1.2 KiB
Python
"""
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974. Subarray Sums Divisible by K
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Difficulty: Medium
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https://leetcode.com/problems/subarray-sums-divisible-by-k/
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──────────────────────────────────────────────────
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Given an integer array nums and an integer k, return the number of
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non-empty subarrays that have a sum divisible by k.
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A subarray is a contiguous part of an array.
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Example 1:
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Input: nums = [4,5,0,-2,-3,1], k = 5
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Output: 7
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Explanation: There are 7 subarrays with a sum divisible by k = 5:
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[4, 5, 0, -2, -3, 1], [5], [5, 0], [5, 0, -2, -3], [0], [0, -2, -3],
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[-2, -3]
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Example 2:
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Input: nums = [5], k = 9
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Output: 0
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Constraints:
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• 1 <= nums.length <= 3 * 10^4
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• -10^4 <= nums[i] <= 10^4
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• 2 <= k <= 10^4
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"""
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class Solution:
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def subarraysDivByK(self, nums: list[int], k: int) -> int:
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remainder_counts = {0: 1}
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cur_sum = 0
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count = 0
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for n in nums:
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cur_sum += n
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remainder = cur_sum % k
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if remainder in remainder_counts:
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count += remainder_counts[remainder]
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remainder_counts[remainder] = remainder_counts.get(remainder, 0) + 1
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return count
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