Program to find smallest intersecting element of each row in a matrix in Python

Suppose we have a 2D matrix where each row is sorted in ascending order. We have to find the smallest number that exists in every row. If there's no such result, then return −1.

So, if the input is like

then the output will be 5

To solve this, we will follow these steps −

• if matrix is empty, then

  • return −1

• first := a new set from first row of matrix

• for each row in matrix, do

  • first := Intersect first a set of elements of row

  • if first is empty, then

    • return −1

• return minimum of first

Let us see the following implementation to get better understanding −

Example

 Live Demo

class Solution:    def solve(self, matrix):       if not matrix:          return -1       first = set(matrix[0])       for row in matrix:          first &= set(row)          if not first:             return -1       return min(first) ob1 = Solution() matrix = [    [2, 3, 5],    [5, 10, 10],    [1, 3, 5] ] print(ob1.solve(matrix))

Input

matrix = [ [2, 3, 5], [5, 10, 10], [1, 3, 5] ]

Output

5