heapq in Python to print all elements in sorted order from row and column wise sorted matrix

Given an n x n matrix, where every row and column is sorted in non-decreasing order. Print all elements of matrix in sorted order. Examples:

Input : mat= [[10, 20, 30, 40],
              [15, 25, 35, 45],
              [27, 29, 37, 48],
              [32, 33, 39, 50]]

Output : Elements of matrix in sorted order
         [10, 15, 20, 25, 27, 29, 30, 32, 
          33, 35, 37, 39, 40, 45, 48, 50]

This problem has existing solution please refer link. We will solve this problem in python with the same approach of merging two sorted arrays using heapq module. 

Implementation:

Python3

# Function to print all elements in sorted order
# from row and column wise sorted matrix
from heapq import merge

def sortedMatrix(mat):

    # initialize result variable with first row of matrix
    result=mat[0]

    # now traverse through complete matrix
    # after first row and merge each row with
    # result one by one
    # after last operation result will contain
    # list of sorted elements of matrix
    for row in mat[1:]:
        result=list(merge(result,row))

    return result

if __name__ == "__main__":
    mat = [[10, 20, 30, 40],
        [15, 25, 35, 45],
        [27, 29, 37, 48],
        [32, 33, 39, 50]]
    print ('Elements of matrix in sorted order')
    print (sortedMatrix(mat))

Output

Elements of matrix in sorted order
[10, 15, 20, 25, 27, 29, 30, 32, 33, 35, 37, 39, 40, 45, 48, 50]

This article is contributed by Shashank Mishra (Gullu). If you like GeeksforGeeks and would like to contribute, you can also write an article using write.geeksforgeeks.org or mail your article to review-team@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks. 

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