题目：

题解：

class Solution:
    def isPerfectSquare(self, num: int) -> bool:
        x0 = num
        while True:
            x1 = (x0 + num / x0) / 2
            if x0 - x1 < 1e-6:
                break
            x0 = x1
        x0 = int(x0)
        return x0 * x0 == num