C Program to Print Boundary Elements of a Matrix

Here, we will print the boundary elements of a matrix using a C program:

Input :
       1 2 3 4  
       1 2 3 4
       1 2 3 4
       1 2 3 4
Output : 
       1 2 3 4 
       1     4 
       1     4 
       1 2 3 4

Approach:

• Traverse the matrix from start to end.
• Assign an outer loop to point to the row and the inner row to traverse the elements of the row.
• if the element lies on the boundary (1st row, 1st column, last row, last column), then print the element, else print a blank space.

Example:

C

// C program to demonstrate the boundary
// element of matrix
#include <stdio.h>

// This function is display the Boundary of matrix
void printBoundary(int mat[][4], int m, int n)
{
    printf("\n Boundary of Matrix \n");
    for (int i = 0; i < m; i++) {
        for (int j = 0; j < n; j++) {
            if (i == 0 || j == 0 || i == n - 1
                || j == n - 1)
                printf(" %d", mat[i][j]);
            else
                printf("  ");
        }
        printf("\n");
    }
}

// Driver code
int main()
{
    int mat[4][4] = { { 1, 2, 3, 4 },
                      { 1, 2, 3, 4 },
                      { 1, 2, 3, 4 },
                      { 1, 2, 3, 4 } };

    printf("\n Input Matrix \n");
    for (int i = 0; i < 4; i++) {
        for (int j = 0; j < 4; j++) {
            printf(" %d", mat[i][j]);
        }
        printf(" \n");
    }

    // printBoundary(a, 4, 4) function accepts a matrix, no
    // of rows and columns as input and display boundaries of
    // matrix
    printBoundary(mat, 4, 4);
    return 0;
}

Output

 Input Matrix 
 1 2 3 4 
 1 2 3 4 
 1 2 3 4 
 1 2 3 4 

 Boundary of Matrix 
 1 2 3 4
 1     4
 1     4
 1 2 3 4

Time Complexity: O(n*n), where n is the size of the array.

Space Complexity: O(1).