python中归并排序

# coding=UTF-8
#!/usr/bin/python

import sys

def merge(nums, first, middle, last):
    "merge"
    #切片边界，左闭右开，从0开始
    lnums = nums[ first:middle+1 ]
    rnums = nums[ middle+1:last+1 ]
    lnums.append(sys.maxint)
    rnums.append(sys.maxint)
    l = 0
    r = 0
    for i in range( first, last+1 ):
        if lnums[l] < rnums[r]:
            nums[i] = lnums[l]
            l+=1
        else:
            nums[i] = rnums[r]
            r+=1

def merge_sort(nums, first, last):
    """mergesort
        mergesort函数中传递的是下标，不是元素的个数
    """28     if first < last:
        middle = (first + last)/2
        #print "middle in loop", count, "is:", middle
        merge_sort(nums, first, middle)
        merge_sort(nums, middle+1, last)
        merge(nums,first, middle, last)
        #print "loops:",count,">>", nums



if __name__ == '__main__':
    nums = [10, 8, 4, -1, 2, 6, 7, 3]
    print "nums is ", nums
    merge_sort(nums, 0, 7)
    print "merge_sort", nums

/usr/bin/python2.7 /root/PycharmProjects/Sort/merge-sort.py
nums is  [10, 8, 4, -1, 2, 6, 7, 3]
merge_sort [-1, 2, 3, 4, 6, 7, 8, 10]

Process finished with exit code 0