我已按照此视频中的指示，实现了最长的常见子序列问题.它只执行第一组代码并产生一个空列表.此实现有什么问题?
I have implemented the longest common subsequence problem as instructed in this video. It just execute first set of code and produces an empty list. What is wrong with this implementation?
def lcs_recursive(xlist,ylist): if not xlist or ylist: return [] x,xs,y,ys, = xlist[0],xlist[1:],ylist[0],ylist[1:] if x == y: return [x] + lcs_recursive(xs,ys) else: return max(lcs_recursive(xlist,ys),lcs_recursive(xs,ylist),key=len) s1 = 'abc' s2 = 'aeb' print lcs_recursive(s1,s2)推荐答案
if not xlist or ylist:将评估为if (not xlist) or (ylist)，因此，如果将Truthy(如非空列表)传递给ylist，它将始终评估为True.您可能想要:
if not xlist or ylist: will evaluate as if (not xlist) or (ylist) and as such if you pass in something Truthy (like a non-empty list) to ylist it will always evaluate to True. You probably want:
if not xlist or not ylist: return []或者，您可以使用:
if not all([xlist, ylist]): return []