Python-如何检查列表的单调性

Question

检查列表单调性的有效方法是什么？
即它具有单调递增或递减的值？

示例：

[0, 1, 2, 3, 3, 4]   # This is a monotonically increasing list
[4.3, 4.2, 4.2, -2]  # This is a monotonically decreasing list
[2, 3, 1]            # This is neither

Answer 1

def strictly_increasing(L):
    return all(x<y for x, y in zip(L, L[1:]))

def strictly_decreasing(L):
    return all(x>y for x, y in zip(L, L[1:]))

def non_increasing(L):
    return all(x>=y for x, y in zip(L, L[1:]))

def non_decreasing(L):
    return all(x<=y for x, y in zip(L, L[1:]))

def monotonic(L):
    return non_increasing(L) or non_decreasing(L)

Answer 2

如果您有大量的数字列表，最好使用numpy，如果您是：

import numpy as np

def monotonic(x):
    dx = np.diff(x)
    return np.all(dx <= 0) or np.all(dx >= 0)

应该会成功的。

Answer 3

import itertools
import operator

def monotone_increasing(lst):
    pairs = zip(lst, lst[1:])
    return all(itertools.starmap(operator.le, pairs))

def monotone_decreasing(lst):
    pairs = zip(lst, lst[1:])
    return all(itertools.starmap(operator.ge, pairs))

def monotone(lst):
    return monotone_increasing(lst) or monotone_decreasing(lst)

这种方法在列表的长度中是O(N)。