有一个新的外语语言使用英语字母.但是,字母之间的顺序你不知道.你得到了外语词典中的字符串单词列表,其中字符串的字符串根据新语言的规则进行词汇分类.返回一个字符串,新外语中独特的字母按照新语言的规则进行词汇分类.如果没有解决方案,返回"".如果有多个解决方案,返回其中任何一个.如果在它们不同的地方的第一个字母,s字符在外语字母 t之前出现,s字符在词汇分类较小.如果第一个 min. (((length, t.length) 字母相同,那么s字符只有如果和s字符较小. ["th: t. Example: words: <wrtf","fzz" Input: Input: <xttzz" Output: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input: Input
解决这个问题使用 Python.
Here's the Python solution to your problem:

```
def alien_order(words):
    # Create a dictionary to store incoming and outgoing edges for each character
    incoming_edges = {char: 0 for word in words for char in word}
    outgoing_edges = {char: set() for word in words for char in word}

    # Add edges to the graph based on adjacent words
    for i in range(len(words) - 1):
        word1 = words[i]
        word2 = words[i + 1]

        if len(word1) > len(word2) and word1.startswith(word2):
            return ""

        for j in range(min(len(word1), len(word2))):
            if word1[j] != word2[j]:
                outgoing_edges[word1[j]].add(word2[j])
                incoming_edges[word2[j]] += 1
                break

    # Perform topological sort
    queue = [char for char in incoming_edges if incoming_edges[char] == 0]
    topo_order = ""
    
    while queue:
        char = queue.pop(0)
        topo_order += char
        
        for next_char in outgoing_edges[char]:
            incoming_edges[next_char] -= 1
            if incoming_edges[next_char] == 0:
                queue.append(next_char)

    if len(topo_order) < len(incoming_edges):
        return ""
        
    return topo_order
```

You can call this function with a list of words to get the unique letters in the new alien language sorted in lexicographically increasing order. For example:

```
words = ["wrt","wrf","er","ett","rftt"]
print(alien_order(words))  # Output: "wertf"
```