leetcode 1079. Letter Tile Possibilities（python）

描述

You have n tiles, where each tile has one letter tiles[i] printed on it.

Return the number of possible non-empty sequences of letters you can make using the letters printed on those tiles.

Example 1:

Input: tiles = "AAB"
Output: 8
Explanation: The possible sequences are "A", "B", "AA", "AB", "BA", "AAB", "ABA", "BAA".	

Example 2:

Input: tiles = "AAABBC"
Output: 188

Example 3:

Input: tiles = "V"
Output: 1

Note:

1 <= tiles.length <= 7
tiles consists of uppercase English letters.

解析

根据题意，只需要找到所有不重复的字符排列组合即可，以后碰到排列组合直接使用 DFS 即可，将所有的排列结果放入 res 中去重得到最终的数量即可。

解答

class Solution(object):
    def numTilePossibilities(self, tiles):
        """
        :type tiles: str
        :rtype: int
        """
        def dfs(path, t):
            if path:
                res.add(path)
            for i in range(len(t)):
                dfs(path+t[i], t[:i]+t[i+1:])
        res = set()
        dfs('', tiles)
        return len(res)

运行结果

Runtime: 116 ms, faster than 48.33% of Python online submissions for Letter Tile Possibilities.
Memory Usage: 23.7 MB, less than 15.00% of Python online submissions for Letter Tile Possibilities.

原题链接：https://leetcode.com/problems/letter-tile-possibilities

您的支持是我最大的动力