Isotonic Step

Problem

Apply one pool-adjacent-violators pass to values with weights, enforcing a non-decreasing fit. Merge adjacent blocks while the previous block mean exceeds the current one.

Return the expanded fitted values (same length as the input); empty input returns [].

Hint

Whenever a block mean drops below its predecessor, average the two blocks together.

Test cases

case 1

in: [[0.2,0.5,0.4],[1,1,1]]

expected: [0.2,0.45,0.45]

case 2

in: [[0.5,0.4,0.3],[1,1,1]]

expected: [0.39999999999999997,0.39999999999999997,0.39999999999999997]

case 3

in: [[0.1,0.2,0.3],[1,1,1]]

expected: [0.1,0.2,0.3]

case 4

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

expected: [1.5,1.5]

case 5

in: [[],[]]

expected: []

Starter codePython

def isotonic_step(values, weights):
    # Your code here
    pass

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