https://www.v2ex.com/t/688786

run.py

from collections import deque #deque是一个实现了双端栈的list，popleft和appendleft。

def battle(bf, l=None, r=None):
#  print('====================')    
  l = l or deque()
  r = r or deque()
  
  temp = deque()
  i = 0
  _len = len(bf)
  bf.append(0)
  while i < _len:
    a = bf[i]
    b = bf[i+1]
    i += 1
    if a > 0 and b < 0:
      i += 1
      if a > -b:
        temp.append(a)
      elif a < -b:
        temp.append(b)
    else:
      temp.append(a)
  bf = temp
#  print(l,bf,r)
  
  while bf and bf[0] < 0:
    l.append(bf.popleft())
    
  while bf and bf[-1] > 0:
    r.appendleft(bf.pop())
#  print(l,bf,r)
  
    
  if bf:
    return battle(bf, l, r)
  else:
    return list(l + r)
    
  
print('>>>>', battle([-1, -2, 3, -4, 5]))
print('>>>>', battle([-3,2,3,-1,-4]))