Dot Product of Sparse Arrays

Problem Statement

You are given two sparse arrays. Your task is to calculate their dot product efficiently.

Design a class named SparseArray with the following features:

• SparseArray(arr): Initializes the object with the array arr
• computeDot(otherArray): Returns the dot product of the current SparseArray instance with another SparseArray instance otherArray

Note: A sparse array contains mostly zero values. You should store the sparse array in a way that uses memory efficiently and allows fast dot product computation.

Examples

Array1 = [2,0,0,1,4], Array2 = [0,5,0,3,0]
Result: 3
Explanation:
sa1 = SparseArray(Array1), sa2 = SparseArray(Array2)
sa1.computeDot(sa2) = 2*0 + 0*5 + 0*0 + 1*3 + 4*0 = 3
    

Array1 = [0,3,0,0,0], Array2 = [0,0,0,0,6]
Result: 0
Explanation:
sa1 = SparseArray(Array1), sa2 = SparseArray(Array2)
sa1.computeDot(sa2) = 0*0 + 3*0 + 0*0 + 0*0 + 0*6 = 0
    

Array1 = [0,2,0,0,1,0,0], Array2 = [4,0,0,0,5,0,7]
Result: 7
Explanation:
sa1 = SparseArray(Array1), sa2 = SparseArray(Array2)
sa1.computeDot(sa2) = 0*4 + 2*0 + 0*0 + 0*0 + 1*5 + 0*0 + 0*7 = 7
    

Constraints

• Length of arrays is between 1 and 90,000 inclusive
• Each element in arrays is between 0 and 120 inclusive