递归与回溯:python列表排列问题

给定一个 没有重复 数字的序列，返回其所有可能的全排列。

class Solution(object):
    def __init__(self):
        self.number_status = list()
        self.total_list = list()

    def permutations(self,number_list,temp=[]):
        if len(temp)==len(number_list):
            self.total_list.append(temp.copy())
            return

        for i in range(len(number_list)):
            if  i >= len(self.number_status):
                self.number_status.append(False)
            if not self.number_status[i]:
                temp.append(number_list[i])
                self.number_status[i] = True
                self.permutations(number_list,temp)
                temp.pop(-1)
                self.number_status[i] = False
        return self.total_list

x=Solution()
total_list = x.permutations([1,2,3])
print(total_list)

output:
[[1, 2, 3], [1, 3, 2], [2, 1, 3], [2, 3, 1], [3, 1, 2], [3, 2, 1]]

给定一个有重复 数字的序列，返回其所有可能的全排列且不重复

class Solution(object):
    def __init__(self):
        self.number_status = list()
        self.total_list = list()

    def permutations2(self,number_list,temp=[]):
        #  如果结果长度和输入长度相等，则添加进结果集
        if len(temp)==len(number_list):
            self.total_list.append(temp.copy())
            return
        number_list.sort()
        for i in range(len(number_list)):
            if  i >= len(self.number_status):  #将数字状态列表补齐至数值列表的长度
                self.number_status.append(False)
            #  如果该元素已经被使用过，则继续遍历
            if not self.number_status[i]:
                #  下一个重复值只有在前一个重复值被使用的情况下才可以使用
                if (i>0 and number_list[i-1] == number_list[i] and not self.number_status[i-1]): continue
                temp.append(number_list[i])
                self.number_status[i] = True
                self.permutations2(number_list,temp)
                temp.pop(-1)
                self.number_status[i] = False
        return self.total_list

x=Solution()
total_list = x.permutations2([1,2,2,2])
print(total_list)

output:
[[1, 2, 2, 2], [2, 1, 2, 2], [2, 2, 1, 2], [2, 2, 2, 1]]