Python中判断完美平方数的正确姿势与常见逻辑陷阱解析

import math

def is_square_flawed(n):
    # 陷阱：此条件判断对n=0时为True，导致提前返回False
    if n == -abs(n):
        return False
    elif math.sqrt(n) != int(math.sqrt(n)):
        return False
    else:
        return True

# 示例测试
print(f"is_square_flawed(0): {is_square_flawed(0)}")   # 预期True，实际False
print(f"is_square_flawed(4): {is_square_flawed(4)}")   # 预期True，实际True
print(f"is_square_flawed(-1): {is_square_flawed(-1)}") # 预期False，实际False

import math

def is_perfect_square(n):
    # 1. 处理负数：负数不是完美平方数
    if n < 0:
        return False

    # 2. 对非负数进行平方根判断
    # math.sqrt(n) 返回浮点数
    # int(math.sqrt(n)) 返回其整数部分
    # 如果两者相等，说明平方根是整数，n是完美平方数
    sqrt_n = math.sqrt(n)
    return sqrt_n == int(sqrt_n)

# 示例测试
print(f"is_perfect_square(0): {is_perfect_square(0)}")       # 预期: True
print(f"is_perfect_square(4): {is_perfect_square(4)}")       # 预期: True
print(f"is_perfect_square(9): {is_perfect_square(9)}")       # 预期: True
print(f"is_perfect_square(16): {is_perfect_square(16)}")     # 预期: True
print(f"is_perfect_square(2): {is_perfect_square(2)}")       # 预期: False
print(f"is_perfect_square(-1): {is_perfect_square(-1)}")     # 预期: False
print(f"is_perfect_square(25.0): {is_perfect_square(25.0)}") # 预期: True (浮点数也可以是完美平方)
print(f"is_perfect_square(26): {is_perfect_square(26)}")     # 预期: False

import math

def is_perfect_square_isqrt(n):
    # 首先处理负数，isqrt只接受非负整数
    if n < 0:
        return False
    # 如果n不是整数，isqrt会抛出TypeError，这里假设n为整数或可转换为整数
    # 如果需要处理浮点数，需要先转换为整数或使用math.sqrt()方法
    if not isinstance(n, int):
        # 针对浮点数输入，可以先转换为整数再判断，或直接使用math.sqrt方法
        # 这里为了演示isqrt的用法，我们假设n为整数
        return False # 或者根据需求处理非整数输入

    # isqrt 返回整数平方根
    # 如果n是完美平方数，则 root * root == n
    # 如果n不是完美平方数，则 root * root < n
    root = math.isqrt(n)
    return root * root == n

# 示例测试
print(f"is_perfect_square_isqrt(0): {is_perfect_square_isqrt(0)}")     # 预期: True
print(f"is_perfect_square_isqrt(4): {is_perfect_square_isqrt(4)}")     # 预期: True
print(f"is_perfect_square_isqrt(9): {is_perfect_square_isqrt(9)}")     # 预期: True
print(f"is_perfect_square_isqrt(2): {is_perfect_square_isqrt(2)}")     # 预期: False
print(f"is_perfect_square_isqrt(-1): {is_perfect_square_isqrt(-1)}")   # 预期: False