131. 分割回文串

class Solution:
    def partition(self, s: str) -> List[List[str]]:
        path,result = [],[] 
        def symmetric_str(path) -> bool:       # 判断是否为回文串；
            is_or_not = True
            for num in path:
                left,right = 0,len(num)-1
                while left<=right and num[left]==num[right]:
                    left += 1
                    right -= 1
                if left <= right: 
                    is_or_not = is_or_not and False
            return is_or_not
        def split_tree(s,start_index):       # 用 分叉树的回溯，解决 组合、分割。
            if start_index>=len(s): 
                if symmetric_str(path):                
                    result.append(path.copy())
                return 
            for i in range(start_index,len(s)):
                path.append(s[start_index:i+1])
                split_tree(s,i+1)
                path.pop()
            return result 
        return split_tree(s,0)