Leetcode #3429: Paint House IV (Readable code solution)

class Solution:
    def minCost(self, numHouses: int, costsToPaint: List[List[int]]) -> int:
        middleIndex = (numHouses / 2)

        calculations = [[] for i in range(numHouses)]
        for i in range(numHouses):
            for j in range(4):
                calculations[i].append([])
                for k in range(4):
                    calculations[i][j].append(-1)

        def calculate(i, previousHouseColor, previousMirroredColor):
            if i >= middleIndex: return 0

            calculatedAlready = (calculations[i][previousHouseColor][previousMirroredColor] != -1)
            if calculatedAlready: return calculations[i][previousHouseColor][previousMirroredColor]

            minResult = math.inf

            # color1 => current (i-th) house
            for color1 in range(3):
                if color1 == previousHouseColor: continue

                # color2 => mirrored house
                for color2 in range(3):
                    if color2 == previousMirroredColor or color2 == color1: continue

                    costToPaint_ith = costsToPaint[i][color1]

                    mirroredIndex = (numHouses - 1 - i)
                    costToPaint_mirrored = costsToPaint[mirroredIndex][color2]

                    costToPaint_next = calculate(i + 1, color1, color2)

                    resultHere = (costToPaint_ith + costToPaint_mirrored + costToPaint_next)
                    minResult = min(minResult, resultHere)

            calculations[i][previousHouseColor][previousMirroredColor] = minResult
            return minResult

        return calculate(0, 3, 3)