Program to find nth smallest number from a given matrix in Python

Suppose we have a 2D matrix, where each row and column is sorted in non-decreasing order, we have to find the nth smallest number.

So, if the input is like

And n = 4, then the output will be 6.

To solve this, we will follow these steps −

• lst := a new list
• for each row i in matrix, do
  • for each cell j in i, do
    • insert j at the end of lst
• sort the list lst
• return lst[n]

Let us see the following implementation to get better understanding −

Example

class Solution:
   def solve(self, matrix, n):
      lst = []
      for i in matrix:
         for j in i:
            lst.append(j)
      lst.sort()
      return lst[n]
ob = Solution()
matrix = [ [2, 4, 30], [3, 4, 31], [6, 6, 32] ]
n = 4
print(ob.solve(matrix, n))

Input

matrix = [
[2, 4, 30],
[3, 4, 31],
[6, 6, 32] ]
n = 4

Output

6