Sparse Matrix Multiplication

Given two sparse integer matrices A and B. Return the result of AB.

Review the rules of multiple two matrices here

Below is a graphical demonstration of matrix multiplication:

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A "sparse" matrix is a matrix where most entries are zero. You may assume that the number of columns in A is equal to that of the number of rows in B.

Input

  • a: an integer matrix.
  • b: an integer matrix.

Output

An integer matrix represent the product of the above matrices.

Examples

Example 1:

Input:

1a = [[1, 0, 3], [0, 1, 2]]
2b = [[0, 1], [1, 3], [0, 0]]

Output: [[0, 1], [1, 3]]

Explanation:

Try it yourself

Solution

Title

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1  >>> a = [1, 2, 3]
2  >>> a[-1]
3  3

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