Contour Area (Shoelace)

Problem

Compute the area of a polygon with the shoelace formula.

Sum the cross products x_i * y_{i+1} - x_{i+1} * y_i around the closed contour, take the absolute value and divide by 2. Round to 4 decimal places.

Hint

Vertex order does not matter because the result is made absolute.

case 1

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

expected: 1

case 2

in: [[[0,0],[2,0],[0,2]]]

expected: 2

case 3

in: [[[0,0],[1,1],[2,2]]]

expected: 0

case 4

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

expected: 1

Starter codePython

def contour_area(points):
    # Your code here
    pass

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