精简Linux文件路径

精简Linux的文件路径：

1. ..回退的功能
2. .留在当前目录
3. //只保留一个/
4. abc/..要返回.
5. 报错
6. 删除最后一个/

主要思路： string.split，注意开始是/或者../或者./等三种不同情况。用栈记录路径的起始位置，讨论/后的不同情况即可：

 

class Solution:
    def linux_path_compress(self, path):
        is_root = path.startswith('/')
        folders = path.split('/')
        f = []
        for folder in folders:
            if (folder == '..'):
                if (not f and is_root):
                    return False, ''
                elif ((not f and not is_root) or (f and f[-1] == '..')):
                    f.append(folder)
                elif (f):
                    f.pop()
            elif (folder and folder != '.'):
                f.append(folder)
        mid = '/'.join(f) + '/'
        prefix = '/' if is_root else './'
        if (f and f[0] == '..'):
            prefix = ''
        return True, prefix + mid

s = Solution()
a = "/.abc/xxx./abc/bacd/.././bcd/fsgs/../../../x/y/z/../../../../.././././xda"
b = "asdf/.abc/xxx./abc/bacd/.././bcd/fsgs/../../../x/y/z/../../../../../../.././../.././././"
c = "/xyz/./bcd/fsgs/../../../x/y/z/../../../.."
d = "../../../etc/xyz/../abc/////////////////////////////.asdf/../../../../"
print(s.linux_path_compress(a)) #(True, '/xda/')
print(s.linux_path_compress(b)) #(True, '../../../')
print(s.linux_path_compress(c)) #(False, '')
print(s.linux_path_compress(d)) #(True, '../../../../')