高阶函数 sorted 的使用

记录一道面试题，对形如x.y.z的版本号进行排序，面试官没有要求从头写排序算法，第一反应是直接用高阶函数sorted进行排序，cmp参数传入比较函数，但是执行报错不支持cmp参数。因为从Python3开始，sorted取消了cmp参数，需要使用functools.cmp_to_key将cmp函数转化为key函数。


def sort_versions(versions):
	# Python2的写法
    return sorted(versions, cmp=cmp_versions)

def cmp_versions(version1, version2):
    version1, version2 = version1.split('.'), version2.split('.')
    p1, p2 = 0, 0
    n1, n2 = len(version1), len(version2)
    while p1 < n1 or p2 < n2:
        num1 = int(version1[p1]) if p1 < n1 else 0
        num2 = int(version2[p2]) if p2 < n2 else 0
        if num1 > num2:
            return 1
        if num1 < num2:
            return -1
        p1 += 1
        p2 += 1
    return 0

versions = ['1.0.1', '2.0.0', '1', '1.0.0', '1.2.3', '0.1.0', '1.12.0', '1.0.10']
print sort_versions(versions)


from functools import cmp_to_key

def sort_versions(versions):
    # Python3的写法
    return sorted(versions, key=cmp_to_key(cmp_versions))

def cmp_versions(version1, version2):
    version1, version2 = version1.split('.'), version2.split('.')
    p1, p2 = 0, 0
    n1, n2 = len(version1), len(version2)
    while p1 < n1 or p2 < n2:
        num1 = int(version1[p1]) if p1 < n1 else 0
        num2 = int(version2[p2]) if p2 < n2 else 0
        if num1 > num2:
            return 1
        if num1 < num2:
            return -1
        p1 += 1
        p2 += 1
    return 0

versions = ['1.0.1', '2.0.0', '1', '1.0.0', '1.2.3', '0.1.0', '1.12.0', '1.0.10']
print(sort_versions(versions))