python - 递归、分治最大子数组

Question

我似乎无法弄清楚为什么我在编译下面突出显示的行时收到错误消息。错误消息是“ValueError:需要超过 2 个值才能解压”...提前感谢您的帮助

def divConHelper(array, first, center, last):
    sumRight = float('-inf') #assign impossibly low number
    sumLeft = float('-inf') #assign impossibly low number
    leftIndexMax = 0
    rightIndexMax = 0 

    # Determine crossover max toward left
    currentLTotal = 0
    for i in range(first, center): 
    #Incrementally add values to sum
      currentLTotal += sum(array[i:center-1])
    #if the total is greater than the sumLeft, replace
      if currentLTotal > sumLeft:
        sumLeft = currentLTotal   
        leftIndexMax = i 

  # Determine crossover max toward right
    currentRTotal=0
    for i in range(center+1, last):
    #Incrementally add values to sum
      currentRTotal += sum(array[center:i+1])
    #if the rightTotal is greater than the sumRight, replace
      if currentRTotal > sumRight:
        sumRight = currentRTotal
        rightIndexMax = i+1 

    bothTotal = sumRight + sumLeft

    return(leftIndexMax, rightIndexMax, bothTotal)
    #return(bothTotal)

def divConMaxSub(self, array, first, last):

    if (last-first) == 0: 
      return array[first: last +1], array[0]


    center = (first+last)// 2
    #Recursive calls to divConMaxSub
    (minA, maxA, sumA) = self.divConMaxSub(array, first, center)
    (minB, maxB, sumB) = self.divConMaxSub(array, center+1, last)
    #call to get max cross values
    (maxL, maxR, maxCross) = divConHelper(array, first, center, last)

    #Calulate the max subarray value
    finalMax = max(sumA, sumB, maxCross)
    #Logic block for return values
    if (finalMax == sumA):
      return array[minA: maxA], sumA
      #return minA, maxA, sumA
    elif (finalMax == sumB):
      return array[minB: maxB], sumB
      #return minB, maxB, sumB
    elif (finalMax == maxCross):
      return array[maxL: maxR], maxCross
      #return maxL, maxR, maxCross 

这是我的主要代码

    from array import *
from utilities import utilities
from algorithms import algorithms  
def main():
   utils = utilities()
   alg = algorithms()
   results = utils.load()
   for line in results:
     max_sub_array, max_sum = alg.simpleenumeration(line)
     utils.printtofile("Simple Enumeration", max_sub_array, max_sum)
     max_sub_array, max_sum = alg.betterenumeration(line)
     utils.printtofile("Better Enumeration", max_sub_array, max_sum)
     max_sub_array, max_sum = alg.divConMaxSub(line)
     utils.printtofile("Divide and Conquer", max_sub_array, max_sum)
     max_sub_array, max_sum = alg.linear_sub_array(line)
     utils.printtofile("Linear sub array", max_sub_array, max_sum)
   #    print("--------------------")

main()

Answer 1

此声明:

return array[minA: maxA], sumA

不返回三个参数(正如您在这段代码中所期望的那样):

(minA, maxA, sumA) = self.divConMaxSub(array, first, center)

它返回数组的一部分作为第一个参数，并将总和作为第二个参数。因此，Python 提示它无法使用 divConMaxSub 的输出来初始化左侧的三个值，因为右侧只有两个值可用。