leetcode 457. 环形数组是否存在循环

class Solution(object):
    def circularArrayLoop(self, nums):
        """
        :type nums: List[int]
        :rtype: bool
        """
        for i in range(0,len(nums)):
            k=[]
            xiabiao=i
            k.append(xiabiao)
            while len(k)<=len(nums):
                xiabiao=(xiabiao+nums[xiabiao])%len(nums)
                if len(k)>1 and xiabiao in k : return True 
                # print xiabiao,nums[xiabiao],nums[k[0]]
                if (nums[xiabiao]>0 and nums[k[0]]>0) or (nums[xiabiao]<0 and nums[k[0]]<0):
                    if nums[xiabiao]%len(nums)==0 :
                        break
                    else:
                        k.append(xiabiao)
                else:
                    break
            # print k
        return False