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7 reverse integer

admin 11月 14, 2020 0

Description

Given a 32-bit signed integer, reverse digits of an integer.
Note:
Assume we are dealing with an environment which could only store integers within the 32-bit signed integer range: [−2^31, 2^31 − 1]. For the purpose of this problem, assume that your function returns 0 when the reversed integer overflows.

My solution

Python

class (object):
def reverse(self, x):
    """
    :type x: int
    :rtype: int
    """
    if x < 0:
        isNegative = True
    elif x > 0:
        isNegative = False
    else:
        return x
    x = str(abs(x))[::-1]
    first = True
    result = ''
    for char in x:
        if char == '0' and first:
            continue
        else:
            first = False
            result = result + char
    x = int(result)
    if isNegative:
        if -x < -2147483648:
            return 0
        else:
            return -x
    else:
        if x > 2147483647:
            return 0
        else:
            return x

想法：转换为字符串进行反转

Best Solution

Python

def reverse(self, x):
    s = cmp(x, 0)
    r = int(`s*x`[::-1])
    return s*r * (r < 2**31)

想法：
1. **意为乘方
2. cmp(x,y) 函数用于比较2个对象，如果 x < y 返回 -1, 如果 x == y 返回 0, 如果 x > y 返回 1