all(map(lambda x:x==-1, series[-i:-mid] * series[-mid:])) # 对折，相乘，全是-1

import numpy as np
import matplotlib.pyplot as plt


# 函数：返回数组尾部对称长度
def symmetry(series):
    for i in range(50, 0, -2):
        mid = i // 2
        is_symmetry = all(map(lambda x:x==-1, series[-i:-mid][::-1] * series[-mid:])) # 对折，相乘，全是-1
        if is_symmetry:
            return i
    return 0


# 计算对称长度
series = np.random.choice([-1, 1], 100)
print(symmetry(series))


# 作图验证
fig, axes = plt.subplots(1, 1, sharex=True)
axes.plot(np.cumsum(series), 'rd-')
plt.show()