merge-sorted-array.py

# Time:  O(n)
# Space: O(1)
#
# 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.
#

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):
        last, i, j = m + n - 1, m - 1, n - 1
        
        while i >= 0 and j >= 0:
            if A[i] > B[j]:
                A[last] = A[i]
                last, i = last - 1, i - 1
            else:
                A[last] = B[j]
                last, j = last - 1, j - 1
        
        while j >= 0:
                A[last] = B[j]
                last, j = last - 1, j - 1

if __name__ == "__main__":
    A = [1, 3, 5, 0, 0, 0, 0]
    B = [2, 4, 6, 7]
    Solution().merge(A, 3, B, 4)
    print A