无法将值存储在全局变量中

Question

我正在尝试使用回溯算法在 leetcode 中解决排列问题，在打印时我得到了所有的可能性，但是当我试图将这些值存储在全局变量中时，我不允许这样做

Ex:
AnswerIwant:[[1,2,3],[1,3,2],[2,1,3],[2,3,1],[3,1,2],[3,2,1]]

when i print those value while recursion it is print 
Example:
[1, 2, 3]
[1, 3, 2]
[2, 3, 1]
[2, 1, 3]
[3, 1, 2]
[3, 2, 1]

当我为 outPut 存储全局变量中的值时，我得到了这样的结果

[1, 2, 3]
[[1, 2, 3]]
[[1, 2]]
[1, 3, 2]
[[1, 3, 2], [1, 3, 2]]
[[1, 3], [1, 3]]
[[1], [1]]
[2, 3, 1]
[[2, 3, 1], [2, 3, 1], [2, 3, 1]]
[[2, 3], [2, 3], [2, 3]]
[2, 1, 3]
[[2, 1, 3], [2, 1, 3], [2, 1, 3], [2, 1, 3]]
[[2, 1], [2, 1], [2, 1], [2, 1]]
[[2], [2], [2], [2]]
[3, 1, 2]
[[3, 1, 2], [3, 1, 2], [3, 1, 2], [3, 1, 2], [3, 1, 2]]
[[3, 1], [3, 1], [3, 1], [3, 1], [3, 1]]
[3, 2, 1]
[[3, 2, 1], [3, 2, 1], [3, 2, 1], [3, 2, 1], [3, 2, 1], [3, 2, 1]]
[[3, 2], [3, 2], [3, 2], [3, 2], [3, 2], [3, 2]]
[[3], [3], [3], [3], [3], [3]]

[[], [], [], [], [], []]

这是我上面输出的代码

nums = [1,2,3]
val=nums
answerIwant = []
numberOfValues=len(val)-1
answer=[]
def permutation(nums, bucket, index,sub):
    global answerIwant,numberOfValues
    for i in range(len(nums)):
        val=nums.pop(0)
        bucket.append(val)
        if len(bucket)-1==numberOfValues:
            print(bucket)
            answerIwant.append(bucket)
        permutation(nums, bucket, index,sub)
        nev=bucket.pop()
        nums.append(nev)
    print(answerIwant)
#[[1,2,3],[1,3,2],[2,1,3],[2,3,1],[3,1,2],[3,2,1]]
sub=[]
bucket = []

val=(permutation(nums, bucket, index,sub))
print(val)

用符号词解释我遇到的问题谢谢

Answer 1

您必须在添加到 answerIwant 列表时附加列表的副本。所以你应该将 answerIwant.append(bucket) 替换为 answerIwant.append(bucket.copy()).

参考this了解更多信息。所以你的代码可能是这样的，

nums = [1,2,3]
val=nums
answerIwant = []
numberOfValues=len(val)-1
answer=[]
def permutation(nums, bucket, index,sub):
    global numberOfValues
    for i in range(len(nums)):
        val=nums.pop(0)
        bucket.append(val)
        if len(bucket)-1==numberOfValues:
            # print(bucket)
            answerIwant.append(bucket.copy())
        permutation(nums, bucket, index,sub)
        nev = bucket
        nev=bucket.pop()
        nums.append(nev)

#[[1,2,3],[1,3,2],[2,1,3],[2,3,1],[3,1,2],[3,2,1]]
sub=[]
bucket = []

permutation(nums, bucket, 0,sub)

print(answerIwant)

无法将值存储在全局变量中

cant store the value in global variable

python

algorithm

recursive-backtracking