Original matrix:
2 4 5 6 
3 4 6 2
6 7 7 2
1 1 1 1
So after swapping the first and last column we get:
6 4 5 2
2 4 6 3
2 7 7 6
1 1 1 1

let temp = mxt[x][0]
mxt[x][0] = mxt[x][size-1]
mxt[x][size-1] = temp

import Foundation
import Glibc

// Size of the array 
var size = 3

// Function to interchange the elements
// of first and last column
func FirstLastColInterchange(M:[[Int]]){
   var mxt : [[Int]] = M

   // Interchanging the elements of first
   // and last column by swapping 
   for x in 0..<size{
      let temp = mxt[x][0]
      mxt[x][0] = mxt[x][size-1]
      mxt[x][size-1] = temp
   }

   // Displaying matrix
   print("Matrix after first and last column interchange:")
   for m in 0..<size{
      for n in 0..<size{
         print(mxt[m][n], terminator: " ")
      }
      print("\n")
   }
}

// Creating 3x3 matrix of integer type
var myMatrix : [[Int]] = [[10, 30, 40], 
   [50, 60, 70], 
   [80, 30, 20]]

print("Original Matrix:")
for x in 0..<size{
   for y in 0..<size{
      print(myMatrix[x][y], terminator:" ")
   }
   print("\n")
}

// Calling the function 
FirstLastColInterchange(M:myMatrix)

Original Matrix:
10 30 40 

50 60 70 

80 30 20 

Matrix after first and last column interchange:
40 30 10 

70 60 50 

20 30 80