LU Pivot Swap Count

Problem

Perform Gaussian elimination with partial pivoting on A and return the number of row swaps performed.

At each column choose the row with the largest absolute pivot and swap it into position before eliminating below it. The swap count determines the sign of the permutation in a PLU factorization.

Hint

Each partial-pivot swap flips the sign of the determinant's permutation factor.

Test cases

case 1

in: [[[2,1],[1,3]]]

expected: 0

case 2

in: [[[1,3],[2,1]]]

expected: 1

case 3

in: [[[0,1],[1,0]]]

expected: 1

case 4

in: [[[1,2,3],[4,5,6],[7,8,9]]]

expected: 2

Starter codePython

def lu_pivot_swaps(A):
    # Your code here
    pass

4 test cases · run your code against them in the editor