并归排序算法（Python 实现）

概念

归并排序是利用归并的思想实现的排序方法，该算法采用了经典的分治（divide-and-conquer）策略（分治法讲问题分成一些小的问题然后递归求解，而治的阶段则讲分的阶段的答案合并到一起，即分而治之）。

过程

code

def merge(left, right):
    result = []
    left_idx = right_idx = 0
    left_over = False
    while True:
        if left[left_idx] < right[right_idx]:
            result.append(left[left_idx])
            left_idx += 1
        else:
            result.append(right[right_idx])
            right_idx += 1
        if left_idx >= len(left):
            left_over = True
            break
        elif right_idx >= len(right):
            break

    if left_over:
        for item in right[right_idx:]:
            result.append(item)
    else:
        for item in left[left_idx:]:
            result.append(item)
    return result


def merge_sort(l):
    if len(l) <= 1:
        return l
    mid_idx = len(l) / 2
    left = merge_sort(l[:mid_idx])
    right = merge_sort(l[mid_idx:])
    return merge(left, right)

Test

def test():
    l = [4, 7, 8, 3, 5, 9, 9, 9, 0, 7, 4, 3, 1, 6]
    print l
    print merge_sort(l)

转载于:https://my.oschina.net/hfanG/blog/2878413