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Python program to sort matrix based upon sum of rows
  • Last Updated : 11 Oct, 2020

Given a Matrix, perform sort based upon the sum of rows.

Input : test_list = [[4, 5], [2, 5, 7], [2, 1], [4, 6, 1]] 
Output : [[2, 1], [4, 5], [4, 6, 1], [2, 5, 7]] 
Explanation : 3 < 9 < 11 < 14. Sorted sum.

Input : test_list = [[4, 5], [2, 5, 7], [4, 6, 1]] 
Output : [[4, 5], [4, 6, 1], [2, 5, 7]] 
Explanation : 9 < 11 < 14. Sorted sum. 

Method #1 : Using sort() + sum()

In this, task of sorting is done using sort(), and computation of sum is done by sum(), and passed as key fnc. to sort().



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# Python3 code to demonstrate working of 
# Sort Matrix by row sum
# Using sort() + sum()
  
# helper_fnc
def sum_sort(row):
      
    # getting sum 
    return sum(row)
  
# initializing list
test_list = [[4, 5], [2, 5, 7], [2, 1], [4, 6, 1]]
  
# printing original list
print("The original list is : " + str(test_list))
  
# using sort() to perform sort
test_list.sort(key = sum_sort)
  
# printing result 
print("Sum sorted Matrix : " + str(test_list))

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Output:

The original list is : [[4, 5], [2, 5, 7], [2, 1], [4, 6, 1]]
Sum sorted Matrix : [[2, 1], [4, 5], [4, 6, 1], [2, 5, 7]]

Method #2 : Using sorted() + sum() + lambda

In this, the task of sorting is done using sorted() and lambda is used in place of the external function call for the key.

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# Python3 code to demonstrate working of
# Sort Matrix by row sum
# Using sorted() + sum() + lambda
  
# initializing list
test_list = [[4, 5], [2, 5, 7], [2, 1], [4, 6, 1]]
  
# printing original list
print("The original list is : " + str(test_list))
  
# using lambda fnction preventing fnc. call
res = sorted(test_list, key=lambda row: sum(row))
  
# printing result
print("Sum sorted Matrix : " + str(res))

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Output:

The original list is : [[4, 5], [2, 5, 7], [2, 1], [4, 6, 1]]
Sum sorted Matrix : [[2, 1], [4, 5], [4, 6, 1], [2, 5, 7]]

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