python - 在 List[int] 中将 0 替换为 01，将 1 替换为 10

Question

我正在努力解决问题K-th Symbol in Grammar - LeetCode

On the first row, we write a 0. Now in every subsequent row, we look at the previous row and replace each occurrence of 0 with 01, and each occurrence of 1 with 10.

Explanation:
row 1: 0
row 2: 01
row 3: 0110
row 4: 01101001

我写了这么一个replace函数

        def replace(row: "List[int]") -> "List[int]":
            """
            rtype: row 
            """
            for i in range(len(row)):
                if row[i] == 0: #0 -> 01
                    row.insert(i+1, 1)
                elif row[i] == 1: #1 -> 10
                    row.insert(i+1, 0)
            return row 

但是，它不能正常工作。

In [3]: r2 = replace([0])                                                                                                     
In [4]: r2                                                                                                                    
Out[4]: [0, 1] 
In [5]: r3 = replace(r2); print(r3)                                                                                           
[0, 1, 0, 1] # correct is [0, 1, 1, 0]
In [6]: r4 = replace(r3); print(r4)                                                                                           
[0, 1, 0, 1, 0, 1, 0, 1] #correct is  ['0', '1', '1', '0', '1', '0', '0', '1']

使用新列表也不行。

    def replace(row: "List[int]") -> "List[int]":
        """
        rtype: row 
        """
        copy = list(row)
        for i in range(len(copy)):
            if copy[i] == 0: #0 -> 01
                row.insert(i+1, 1)
            elif copy[i] == 1: #1 -> 10
                row.insert(i+1, 0)
        return row 

有什么问题？

Answer 1

将str.join与dict一起使用:

a = '0'
d = {'0': '01', '1': '10'}
# Now run below line only
a = ''.join(d[s] for s in a)
a

输出:

01
0110
01101001
...