Question

Hello I am writing and testing a recursive dynamic programmed knapsack (0-1) (the following code is the main file and the function) I keep getting the error (which is posted after the code)…I am really confused as to what the error is so any help will be much appreciated!

MAIN FILE

import Knapsack_Test

size = 10
W = 2**size
knapsack = Knapsack_Test.Knapsack_Test()

for i in range(1, 10):
    knapsack.recursive_knapsack_test(size, W)
size = size + 100*i

W = 2**size

FUNCTION CALLING (WHICH IS IN CLASS Knapsack_Test.py

def recursive_dynamic_knap(self, v, w, i, W):
    n = len(v) - 1
    if i == n:
        if W < w[n]:
            return 0
        else:
            return v
    elif W < w[i]:
        return self.recursive_dynamic_knap(v, w, i+1, W)

    return max(self.recursive_dynamic_knap(v, w, i+1,W), self.recursive_dynamic_knap(v, w, i+1, W-w[i]) + v[i])

ERROR

Traceback (most recent call last):
  File "\\minerfiles.mst.edu\dfs\users\asadmb\Desktop\Programming 3\Knapsack_Main.py", line 9, in <module>
    knapsack.recursive_knapsack_test(size, W)
  File "\\minerfiles.mst.edu\dfs\users\asadmb\Desktop\Programming 3\Knapsack_Test.py", line 19, in recursive_knapsack_test
    self.knapsack.recursive_dynamic_knap(v, w, j, W)
  File "\\minerfiles.mst.edu\dfs\users\asadmb\Desktop\Programming 3\KnapsackClass.py", line 22, in recursive_dynamic_knap
    return max(self.recursive_dynamic_knap(v, w, i+1,W), self.recursive_dynamic_knap(v, w, i+1, W-w[i]) + v[i])
  File "\\minerfiles.mst.edu\dfs\users\asadmb\Desktop\Programming 3\KnapsackClass.py", line 22, in recursive_dynamic_knap
    return max(self.recursive_dynamic_knap(v, w, i+1,W), self.recursive_dynamic_knap(v, w, i+1, W-w[i]) + v[i])
  File "\\minerfiles.mst.edu\dfs\users\asadmb\Desktop\Programming 3\KnapsackClass.py", line 22, in recursive_dynamic_knap
    return max(self.recursive_dynamic_knap(v, w, i+1,W), self.recursive_dynamic_knap(v, w, i+1, W-w[i]) + v[i])
  File "\\minerfiles.mst.edu\dfs\users\asadmb\Desktop\Programming 3\KnapsackClass.py", line 22, in recursive_dynamic_knap
    return max(self.recursive_dynamic_knap(v, w, i+1,W), self.recursive_dynamic_knap(v, w, i+1, W-w[i]) + v[i])
  File "\\minerfiles.mst.edu\dfs\users\asadmb\Desktop\Programming 3\KnapsackClass.py", line 22, in recursive_dynamic_knap
    return max(self.recursive_dynamic_knap(v, w, i+1,W), self.recursive_dynamic_knap(v, w, i+1, W-w[i]) + v[i])
  File "\\minerfiles.mst.edu\dfs\users\asadmb\Desktop\Programming 3\KnapsackClass.py", line 22, in recursive_dynamic_knap
    return max(self.recursive_dynamic_knap(v, w, i+1,W), self.recursive_dynamic_knap(v, w, i+1, W-w[i]) + v[i])
  File "\\minerfiles.mst.edu\dfs\users\asadmb\Desktop\Programming 3\KnapsackClass.py", line 22, in recursive_dynamic_knap
    return max(self.recursive_dynamic_knap(v, w, i+1,W), self.recursive_dynamic_knap(v, w, i+1, W-w[i]) + v[i])
TypeError: unorderable types: int() > list()

Answer 1

I believe the problem is that in return max(self.recursive_dynamic_knap(v, w, i+1,W), self.recursive_dynamic_knap(v, w, i+1, W-w[i]) + v[i]) one of the calls to recursive_dynamic_knap is returning v, which is a list, and which makes no sense as an argument to max() because it is “unorderable” (can’t sensibly be judged to be greater than or less than an int)