【leetcode】Merge Sorted Array

題目描述

Given two sorted integer arrays A and B, merge B into A as one sorted array.

Note:
You may assume that A has enough space (size that is greater or equal to m + n) to hold additional elements from B. The number of elements initialized in A and B are m and n respectively.

解題思路：

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(void)
    def merge(self, A, m, B, n):
        posa = m - 1
        posb = n - 1
        for i in range(m+n-1,-1,-1):
            if posa < 0:
                A[i] = B[posb]
                posb -= 1
            elif posb < 0:
                return
            elif A[posa] > B[posb]:
                A[i] = A[posa]
                posa -= 1
            else:
                A[i] = B[posb]
                posb -= 1