523. Continuous Subarray Sum

Given a list of non-negative numbers and a target integer k, write a function to check if the array has a continuous subarray of size at least 2 that sums up to a multiple of k , that is, sums up to n*k where n is also an integer.

Example 1:

Input: [23, 2, 4, 6, 7],  k=6
Output: True
Explanation: Because [2, 4] is a continuous subarray of size 2 and sums up to 6.

Example 2:

Input: [23, 2, 6, 4, 7],  k=6
Output: True
Explanation: Because [23, 2, 6, 4, 7] is an continuous subarray of size 5 and sums up to 42.

Constraints:

• The length of the array won't exceed 10,000.
• You may assume the sum of all the numbers is in the range of a signed 32-bit integer.

# @lc code=start
using LeetCode

function check_subarray_sum(nums::Vector{Int}, k::Int)
    pushfirst!(nums, 0)
    cumsum!(nums, nums)
    nums .%= k
    st = Set{Int}()
    len = length(nums)
    for i in 3:len
        nums[i] ∈ st && return true
        push!(st, nums[i - 1])
    end
    return false
end
# @lc code=end

check_subarray_sum (generic function with 1 method)

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