# Replace the middle element of matrix with sum of surrounding elements

Given a square matrix mat[][] of odd dimensions, the task is to change the value of the middle most element of the matrix to the sum of the elements surrounding it.

Examples:

Input:
mat[][] = { {2, 1, 7},
{3, 7, 2},
{5, 4, 9} }
Output:
2 1 7
3 10 2
5 4 9

Input:
mat[][] = {{1, 3, 5, 6, 7},
{3, 5, 3, 2, 1},
{1, 2, 3, 4, 5},
{7, 9, 2, 1, 6},
{9, 1, 5, 3, 2} }
Output:
1 3 5 6 7
3 5 3 2 1
1 2 11 4 5
7 9 2 1 6
9 1 5 3 2

## Recommended: Please try your approach on {IDE} first, before moving on to the solution.

Approach: The middle element of the matrix of odd order will be located at the position mat[n / 2][n / 2].

Therefore directly update the element as:

mat[n / 2][n / 2] = mat[n / 2 - 1][n / 2]
+ mat[n / 2][n / 2 - 1]
+ mat[n / 2 + 1][n / 2]
+ mat[n / 2][n / 2 + 1]

Below is the implementation of the above approach:

## C++

 // C++ program to replace the value of the middle element  // of the matrix with the sum of surrounding elements    #include using namespace std; const int MAX = 100;    // Function to print the matrix void print(int mat[][MAX], int n) {     for (int i = 0; i < n; i++) {         for (int j = 0; j < n; j++) {             cout << mat[i][j] << " ";         }         cout << endl;     } }    // Function to change the value of the middle element  // of the matrix to the sum of surrounding elements void changemiddle(int mat[][MAX], int n) {     // Change the middle element     mat[n / 2][n / 2]         = mat[n / 2 - 1][n / 2]           + mat[n / 2][n / 2 - 1]           + mat[n / 2 + 1][n / 2]           + mat[n / 2][n / 2 + 1];        // Function call to print the matrix     print(mat, n); }    // Driver code int main() {     int mat[][MAX] = { { 2, 1, 7 },                        { 3, 7, 2 },                        { 5, 4, 9 } };        changemiddle(mat, 3);        return 0; }

## Java

 // Java program to replace the value of the middle element  // of the matrix with the sum of surrounding elements\    public class GFG{            // Function to print the matrix     static void print(int mat[][], int n)     {         for (int i = 0; i < n; i++) {             for (int j = 0; j < n; j++) {                 System.out.print(mat[i][j] + " ");             }              System.out.println();         }     }            // Function to change the value of the middle element      // of the matrix to the sum of surrounding elements     static void changemiddle(int mat[][], int n)     {         // Change the middle element         mat[n / 2][n / 2]             = mat[n / 2 - 1][n / 2]               + mat[n / 2][n / 2 - 1]               + mat[n / 2 + 1][n / 2]               + mat[n / 2][n / 2 + 1];                // Function call to print the matrix         print(mat, n);     }            // Driver code     public static void main(String []args)     {         int mat[][] = { { 2, 1, 7 },                            { 3, 7, 2 },                            { 5, 4, 9 } };                changemiddle(mat, 3);     }     // This code is contributed by Ryuga }

## Python3

 # Python3 program to replace the value # of the middle element of the matrix  # with the sum of surrounding elements     MAX = 100    # Function to print the matrix  def printMatrix(mat, n):         for i in range(n):          for j in range(n):              print(mat[i][j], end = " ")                     print()    # Function to change the value of  # the middle element of the matrix # to the sum of surrounding elements  def changemiddle(mat, n):        # Change the middle element      mat[n // 2][n // 2] = (mat[n // 2 - 1][n // 2] +                             mat[n // 2][n // 2 - 1] +                             mat[n // 2 + 1][n // 2] +                             mat[n // 2][n // 2 + 1])        # Function call to print the matrix      printMatrix(mat, n)     # Driver Code if __name__ == "__main__":         mat = [ [ 2, 1, 7 ],              [ 3, 7, 2 ],              [ 5, 4, 9 ]]         changemiddle(mat, 3)    # This code is contributed  # by rituraj_jain

## C#

 // C# program to replace the value of the middle element  // of the matrix with the sum of surrounding elements\     using System; public class GFG{             // Function to print the matrix     static void print(int[,] mat, int n)     {         for (int i = 0; i < n; i++) {             for (int j = 0; j < n; j++) {                 Console.Write(mat[i,j] + " ");             }              Console.Write("\n");         }     }             // Function to change the value of the middle element      // of the matrix to the sum of surrounding elements     static void changemiddle(int[,] mat, int n)     {         // Change the middle element         mat[n / 2,n / 2]             = mat[n / 2 - 1,n / 2]               + mat[n / 2,n / 2 - 1]               + mat[n / 2 + 1,n / 2]               + mat[n / 2,n / 2 + 1];                 // Function call to print the matrix         print(mat, n);     }             // Driver code     public static void Main()     {         int[,] mat = { { 2, 1, 7 },                            { 3, 7, 2 },                            { 5, 4, 9 } };                 changemiddle(mat, 3);     }       }

## PHP



Output:

2 1 7
3 10 2
5 4 9

Time Complexity : O(n * m), Here n is No. of Rows and m is No. of Colum.

My Personal Notes arrow_drop_up

Check out this Author's contributed articles.

If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.

Please Improve this article if you find anything incorrect by clicking on the "Improve Article" button below.

Article Tags :
Practice Tags :

Be the First to upvote.

Please write to us at contribute@geeksforgeeks.org to report any issue with the above content.