从带有条件参数的列表列表中减去列表列表

Question

我遇到了一个很难解决的棘手问题。

我有两个列表列表：

firstList = [[0, 9], [0, 4], [0]]
secondList = [[18], [19, 7], [20]]

我想按升序从 secondList 中的值中减去 firstList 中的值，但是仅如果 firstList 还没有 "used"。例如：

thirdList = [0,4]
fourthList = [19,7]
emptyList = []

emptyList.append(fourthList-thirdList]
print(emptyList)
>>>[7,3]

在这种情况下，未使用 19，因为在 fourthList 中的先前值和 19

之间的 thirdList 中没有值

我在想这样的事情（虽然它很快分解成伪代码）

firstList = [[0, 9], [0, 4], [0]]
secondList = [[18], [19, 7], [20]]
emptyList = [ [] for y in range(3) ]

for x in range(3) :
    #for smallest value in secondList[x], subtract all smaller values in firstList and then delete them, append values to emptyList[x]
    #for next smallest value in secondList[x], subtract all smaller values in firstList and then delete them, append values to emptyList[x]
    #repeat until firstList is empty, then exit loop

print(emptyList)
>>>[[9, 18], [3, 7], [20]]

这将排除在 secondList[1] 中使用 19，因为 0 和 4 在从 7[=22= 中减去之后已经被删除]

Answer 1

firstList = [[0, 9], [0, 4], [0]]
secondList = [[18], [19, 7], [20]]
all_results = []

for x in range(0, len(firstList)):  
    values_of_first = firstList[x]
    values_of_second = secondList[x]
    values_of_first.sort()
    values_of_second.sort()  
    tmp_results = []

    for subtractor in values_of_second:    
        used_values = []
        for subtracted in values_of_first:
            if subtracted >= subtractor:
                break
            else:
                used_values.append(subtracted)
                tmp_results.append(subtractor - subtracted)

        for used_value in used_values:
            values_of_first.remove(used_value)

    tmp_results.sort()
    all_results.append(tmp_results)

它产生all_results == [[9, 18], [3, 7], [20]]

从带有条件参数的列表列表中减去列表列表

subtract list of lists from list of lists with conditional arguments

python

for-loop

subtraction

nested-lists

conditional-statements