合并并使用排序合并排序列表 [英] Merge and sort a list using merge sort

问题描述

这是我的code

def merge_lists(all_lst):
    if len(all_lst) < 2:
        return all_lst[0]   # get rid of the extra [] 
    left = merge_lists(all_lst[:len(all_lst)//2]) #[[2, 7, 10]]  ##[[0, 4, 6]]      
    right = merge_lists(all_lst[len(all_lst)//2:])#[[0, 4, 6], [3, 11]] ##[[3,11]]
    def merge(left,right):
        results = []
        while left and right:
            if left[0] < right[0]:
                results.append(left[0])
                left.remove(left[0])
            else:
                results.append(right[0])
                right.remove(right[0])
        results.extend(left)
        results.extend(right)
        return results
    return merge(left, right) 

我能够得到答案，当我把这个

I am able to get the answer when i put this

all_lst = [[2, 7, 10], [0, 4, 6], [3, 11]]
print(merge_lists(all_lst)) # [0, 2, 3, 4, 6, 7, 10, 11]

但是，当我试图改变它一点尚不工作

But when I tried to change it a little it doesn't work already

 all_lst = [[2, 7, 10], [0, 4, 6], [3, 11, 1]]
print(merge_lists(all_lst)) ##[0, 2, 3, 4, 6, 7, 10, 11, 1]

我想知道什么是错

May I know what's wrong

推荐答案

第三个列表进行排序。当你做你的最后延长1插入 最终列表的末尾。 你叫合并之前，您应该排序您的名单。

The third list is not sorted. When you do your final extend the 1 is inserted into the end of the final list. You should sort your lists before you call merge.

换句话说，你的投入应该是：

In other words your input should be:

 all_lst = [[2, 7, 10], [0, 4, 6], [1, 3, 11]]

他们的方式合并工作原理是，假设子列表是有序的。

They way merging works is that assumes that the sublists are ordered.

例如把那些两个列表：

left = [1, 3]
right = [2, 4]
results = []    

合并是这样的：

merging goes like this:

if left[0] < right[0]:
    results.append(left[0])
    left.remove(left[0])

所以现在

results = [1]
left = [3]
right = [2,4]

但如果你有：

but if you had:

left = [3, 1]
right = [2, 4]
results = []   

合并是这样的：

merging goes like this:

if left[0] < right[0]: #false
else:
    results.append(right[0])
    right.remove(right[0])

所以现在

results = [2]
left = [3,1]
right = [4]

所以你结束了一个无序的最终名单。

therefore you end up with an unordered final list.

这篇关于合并并使用排序合并排序列表的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！