题解 | #牛群排列#

#
# 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
#
# 
# @param s string字符串 
# @return string字符串一维数组
#
class Solution:
    def cowPermutations(self , s: str) -> List[str]:
        # write code here
        s=sorted(s)
        res=[]
        vis=set()

        def backtrack(path):
            if len(path) == len(s):
                res.append(path)

            for i in range(len(s)):
                if i in vis:
                    continue
                vis.add(i)
                backtrack(path+s[i])
                vis.remove(i)

        backtrack("")
        return res