AlgoDatSoSe24/SoSe24/lec02_maxfolge/divide_et_impera.py

from SoSe24.algodat.foundation import AlgoDatArray, AlgoDatValue, read_int_sequence, MinusInf
from time import perf_counter as pfc
def in_between(z: AlgoDatArray, l: int, m: int, r: int) -> (AlgoDatValue, int, int):
    left_max = AlgoDatValue(MinusInf())
    left = AlgoDatValue(0)
    current_sum = AlgoDatValue(0)
    for i in range(m, l - 1, -1):
        current_sum += z[i]
        if current_sum > left_max:
            left_max.value = current_sum.value
            left.value = i
    right_max = AlgoDatValue(MinusInf())
    right = AlgoDatValue(0)
    current_sum.value = 0
    for i in range(m + 1, r + 1):
        current_sum += z[i]
        if current_sum > right_max:
            right_max.value = current_sum.value
            right.value = i
    return left_max + right_max, left, right

def maxfolge_part(z: AlgoDatArray, l:int, r:int) -> (int, int, int):
    if l == r:
        return z[l].value, l, r
    m = (l + r) // 2
    left_sum, left_left, left_right = maxfolge_part(z, l, m)
    right_sum, right_left, right_right = maxfolge_part(z, m + 1, r)
    cross_sum, cross_left, cross_right = in_between(z, l, m, r)
    if left_sum >= right_sum and left_sum >= cross_sum:
        return left_sum, left_left, left_right
    elif right_sum >= left_sum and right_sum >= cross_sum:
        return right_sum, right_left, right_right
    else:
        return cross_sum, cross_left, cross_right

def maxfolge3(z: AlgoDatArray) -> (int, int, int):
    return maxfolge_part(z, 0, z.size - 1)

if __name__ == "__main__":
    z = read_int_sequence("../../seq3.txt")
    start = pfc()
    print(maxfolge3(z))
    print(f"Dauer: {pfc() - start:.4f}s")
    AlgoDatValue.summary()