10_Subarray_Sums_Divisible_By_K

class Solution:
    def subarraysDivByK(self, nums: List[int], k: int) -> int:
        d=defaultdict(int)
        # d[0]=-1
        s=0
        ans=0
        for i in range(len(nums)):
            s=(s+nums[i])%k
            d[s]+=1
            if s==0:
                ans+=d[s]
            else:
                ans+=d[s]-1
        # print(d)
        return ans