剑指offer-栈的压入弹出序列21

class Solution:
    def IsPopOrder(self, pushV, popV):
        # write code here 
        lenpushV=len(pushV)
        lenpopV=len(popV)
        i=0
        j=0
        stack=[]
        while i<lenpushV:
            stack.append(pushV[i])
            while len(stack) is not 0 and stack[-1]==popV[j]:
                stack.pop(-1)
                j+=1
            i+=1
        if len(stack)==0:
            return True
        else:
            return False