Leetcode: Merge Sorted Array @Python

Merge from the end so that the index of the elements won't change before merging.

class Solution:
    # @param A  a list of integers
    # @param m  an integer, length of A
    # @param B  a list of integers
    # @param n  an integer, length of B
    # @return nothing
    def merge(self, A, m, B, n):
        i,j,k=m-1,n-1,m+n-1
        while i>=0 and j>=0:
            if A[i]>B[j]:
                A[k]=A[i]
                i-=1
            else:
                A[k]=B[j]
                j-=1
            k-=1
        while j>=0:
            A[k]=B[j]
            j-=1
            k-=1