class SparseVector:
    # Constructor for sparseVector.
    def __init__(self, nums: List[int]) -> None:
        # write your code here

        self.pairs = []
        for ind, num in enumerate(nums):
            if num:
                self.pairs.append([ind, num])


    def dotProduct(self, vec) -> int:
        # write your code here

        p = 0
        q = 0
        result = 0
        while p < len(self.pairs) and q < len(vec.pairs):
            if self.pairs[p][0] == vec.pairs[q][0]:
                result += self.pairs[p][1]*vec.pairs[q][1]
                p = p + 1
                q = q + 1
            elif self.pairs[p][0] < vec.pairs[q][0]:
                p = p + 1
            else:
                q = q + 1

        return result