去掉len(s)==0这个条件,直接把辅助栈底弄为-1,嘿嘿

class Solution:
    def IsPopOrder(self , pushV: List[int], popV: List[int]) -> bool:
        n = len(pushV)
        s= [-1]
        j=0
        for i in range(n):
            while j<n and ( s[-1] != popV[i]):
                s.append(pushV[j])
                j+=1
            if s[-1] == popV[i]:
                s.pop()
            else :
                return False
        return True