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Decode the Coding Interview in Java: Real-World Examples

Sparse Matrix Multiplication

Understand how to multiply two sparse matrices by converting them into hashmaps that store only non-zero elements. This lesson teaches you to implement an efficient solution by iterating over these hashmaps and computing the resulting matrix with improved performance.

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Description

We have two sparse matrices, A and B.

“A sparse matrix is one in which most of the elements are zero.”

You need to multiply the two matrices and return the output matrix. You can assume that A’s column number is equal to B’s row number.

Constraints

The following are some constraints:

  • 1 <= A.length, B.length <= 100
  • 1 <= A[i].length, B[i].length <= 100
  • -100 <= A[i][j], B[i][j] <= 100

Let’s review this scenario using the example below:

Coding exercise

Java
class Solution {

    public static int[][] multiply(int[][] A, int[][] B){

        // Your code goes here;

        int[][] C = {};

        return C;

    }

}
Sparse Matrix Multiplication

Solution

We have two sparse matrices, meaning most of the matrices’ elements ...