Python循环删除列表-质数下标

删除列表会导致下标不断变换，加入counter来计算前面删了几个数，每次删除时用原先的index-counter即可

class Solution:
    def getNumber(self, a: List[int]) -> int:
        
        def is_prime(num):
            base = 2
            if num == 1:
                return False
            elif num in (2,3):
                return True
            while base < num:
                if num % base == 0:
                    return False
                base += 1
            return True
        
        
        if len(a) == 1:
            return a[0]
        length = len(a)
        counter = 0
        index = 0
        while index < length:
            if is_prime(index):
                i = index - counter
                a.pop(i)
                counter += 1
            index += 1
        return self.getNumber(a)