Boundary elements of a Matrix

Printing Boundary Elements of a Matrix.

Examples:

Input : 1 2 3 4  
        5 6 7 8
        1 2 3 4
        5 6 7 8
Output : 1 2 3 4 
         5     8 
         1     4 
         5 6 7 8

Recommended: Please solve it on “PRACTICE ” first, before moving on to the solution.

The idea is really simple. We traverse given matrix. For every element being traversed, we print it if it is a corner element. If it is not a corner element, then we print space character.

C++

// C++ program to print boundary element of 
// matrix. 
#include <bits/stdc++.h> 
using namespace std; 
  
const int MAX = 100; 
  
void printBoundary(int a[][MAX], int m, int 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) 
                cout << a[i][j] << " "; 
            else
                cout << " "
                     << " "; 
        } 
        cout << "\n"; 
    } 
} 
  
// Driver code 
int main() 
{ 
    int a[4][MAX] = { { 1, 2, 3, 4 }, { 5, 6, 7, 8 }, { 1, 2, 3, 4 }, { 5, 6, 7, 8 } }; 
    printBoundary(a, 4, 4); 
    return 0; 
} 

Java

// JAVA Code for Boundary elements of a Matrix 
class GFG { 
  
    public static void printBoundary(int a[][], int m, 
                                     int n) 
    { 
        for (int i = 0; i < m; i++) { 
            for (int j = 0; j < n; j++) { 
                if (i == 0) 
                    System.out.print(a[i][j] + " "); 
                else if (i == m - 1) 
                    System.out.print(a[i][j] + " "); 
                else if (j == 0) 
                    System.out.print(a[i][j] + " "); 
                else if (j == n - 1) 
                    System.out.print(a[i][j] + " "); 
                else
                    System.out.print("  "); 
            } 
            System.out.println(""); 
        } 
    } 
  
    /* Driver program to test above function */
    public static void main(String[] args) 
    { 
        int a[][] = { { 1, 2, 3, 4 }, { 5, 6, 7, 8 }, { 1, 2, 3, 4 }, { 5, 6, 7, 8 } }; 
  
        printBoundary(a, 4, 4); 
    } 
} 
// This code is contributed by Arnav Kr. Mandal. 

Python

# Python program to print boundary element 
# of matrix. 
  
MAX = 100
   
def printBoundary(a, m, n): 
    for i in range(m): 
        for j in range(n): 
            if (i == 0): 
                print a[i][j], 
            elif (i == m-1): 
                print a[i][j], 
            elif (j == 0): 
                print a[i][j], 
            elif (j == n-1): 
                print a[i][j], 
            else: 
                print " ", 
        print
          
# Driver code 
a = [ [ 1, 2, 3, 4 ], [ 5, 6, 7, 8 ],  
    [ 1, 2, 3, 4 ], [ 5, 6, 7, 8 ] ] 
printBoundary(a, 4, 4) 
  
# This code is contributed by Sachin Bisht 

C#

// C# Code for Boundary 
// elements of a Matrix 
using System; 
  
class GFG { 
  
    public static void printBoundary(int[, ] a, 
                                     int m, 
                                     int n) 
    { 
        for (int i = 0; i < m; i++) { 
            for (int j = 0; j < n; j++) { 
                if (i == 0) 
                    Console.Write(a[i, j] + " "); 
                else if (i == m - 1) 
                    Console.Write(a[i, j] + " "); 
                else if (j == 0) 
                    Console.Write(a[i, j] + " "); 
                else if (j == n - 1) 
                    Console.Write(a[i, j] + " "); 
                else
                    Console.Write("  "); 
            } 
            Console.WriteLine(" "); 
        } 
    } 
  
    // Driver Code 
    static public void Main() 
    { 
        int[, ] a = { { 1, 2, 3, 4 }, 
                      { 5, 6, 7, 8 }, 
                      { 1, 2, 3, 4 }, 
                      { 5, 6, 7, 8 } }; 
  
        printBoundary(a, 4, 4); 
    } 
} 
  
// This code is contributed by ajit 

PHP

<?php 
// PHP program to print  
// boundary element of  
// matrix. 
$MAX = 100; 
  
function printBoundary($a, $m, $n) 
{ 
    global $MAX; 
    for ($i = 0; $i < $m; $i++)  
    { 
        for ($j = 0; $j < $n; $j++)  
        { 
            if ($i == 0) 
                echo $a[$i][$j], " "; 
            else if ($i == $m - 1) 
                echo $a[$i][$j], " "; 
            else if ($j == 0) 
                echo $a[$i][$j], " "; 
            else if ($j == $n - 1) 
                echo $a[$i][$j], " "; 
            else
                echo " ", " "; 
        } 
        echo "\n"; 
    } 
} 
  
// Driver code 
$a = array(array( 1, 2, 3, 4 ),  
           array( 5, 6, 7, 8 ),  
           array( 1, 2, 3, 4 ),  
           array( 5, 6, 7, 8 )); 
printBoundary($a, 4, 4); 
      
// This code is contributed  
// by akt_mit 
?> 

Output:

Finding sum of boundary elements

Examples:

Input : 1 2 3 4  
        5 6 7 8
        1 2 3 4
        5 6 7 8
Output : 54

C++

// C++ program to find sum of boundary elements 
// of matrix. 
#include <bits/stdc++.h> 
using namespace std; 
  
const int MAX = 100; 
  
int getBoundarySum(int a[][MAX], int m, int n) 
{ 
    long long int sum = 0; 
    for (int i = 0; i < m; i++) { 
        for (int j = 0; j < n; j++) { 
            if (i == 0) 
                sum += a[i][j]; 
            else if (i == m - 1) 
                sum += a[i][j]; 
            else if (j == 0) 
                sum += a[i][j]; 
            else if (j == n - 1) 
                sum += a[i][j]; 
        } 
    } 
    return sum; 
} 
  
// Driver code 
int main() 
{ 
    int a[][MAX] = { { 1, 2, 3, 4 }, { 5, 6, 7, 8 }, { 1, 2, 3, 4 }, { 5, 6, 7, 8 } }; 
    long long int sum = getBoundarySum(a, 4, 4); 
    cout << "Sum of boundary elements is " << sum; 
    return 0; 
} 

Java

// JAVA Code for Finding sum of boundary elements 
class GFG { 
  
    public static long getBoundarySum(int a[][], int m, 
                                      int n) 
    { 
        long sum = 0; 
        for (int i = 0; i < m; i++) { 
            for (int j = 0; j < n; j++) { 
                if (i == 0) 
                    sum += a[i][j]; 
                else if (i == m - 1) 
                    sum += a[i][j]; 
                else if (j == 0) 
                    sum += a[i][j]; 
                else if (j == n - 1) 
                    sum += a[i][j]; 
            } 
        } 
        return sum; 
    } 
  
    /* Driver program to test above function */
    public static void main(String[] args) 
    { 
        int a[][] = { { 1, 2, 3, 4 }, { 5, 6, 7, 8 }, { 1, 2, 3, 4 }, { 5, 6, 7, 8 } }; 
        long sum = getBoundarySum(a, 4, 4); 
        System.out.println("Sum of boundary elements"
                           + " is " + sum); 
    } 
} 
// This code is contributed by Arnav Kr. Mandal. 

Python

# Python program to print boundary element  
# of matrix. 
  
MAX = 100
   
def printBoundary(a, m, n): 
    sum = 0
    for i in range(m): 
        for j in range(n): 
            if (i == 0): 
                sum += a[i][j] 
            elif (i == m-1): 
                sum += a[i][j] 
            elif (j == 0): 
                sum += a[i][j] 
            elif (j == n-1): 
                sum += a[i][j] 
    return sum
      
# Driver code 
a = [ [ 1, 2, 3, 4 ], [ 5, 6, 7, 8 ], 
    [ 1, 2, 3, 4 ], [ 5, 6, 7, 8 ] ] 
sum = printBoundary(a, 4, 4) 
print "Sum of boundary elements is", sum
  
# This code is contributed by Sachin Bisht 

C#

// C# Code for Finding sum 
// of boundary elements 
using System; 
  
class GFG { 
    public static long getBoundarySum(int[, ] a, 
                                      int m, int n) 
    { 
        long sum = 0; 
        for (int i = 0; i < m; i++) { 
            for (int j = 0; j < n; j++) { 
                if (i == 0) 
                    sum += a[i, j]; 
                else if (i == m - 1) 
                    sum += a[i, j]; 
                else if (j == 0) 
                    sum += a[i, j]; 
                else if (j == n - 1) 
                    sum += a[i, j]; 
            } 
        } 
        return sum; 
    } 
  
    // Driver Code 
    static public void Main() 
    { 
        int[, ] a = { { 1, 2, 3, 4 }, 
                      { 5, 6, 7, 8 }, 
                      { 1, 2, 3, 4 }, 
                      { 5, 6, 7, 8 } }; 
        long sum = getBoundarySum(a, 4, 4); 
        Console.WriteLine("Sum of boundary"
                          + " elements is " + sum); 
    } 
} 
  
// This code is contributed by ajit 

PHP

<?php 
// PHP program to find  
// sum of boundary  
// elements of matrix. 
  
function getBoundarySum($a,  
                        $m, $n) 
{ 
    $sum = 0; 
    for ($i = 0; $i < $m; $i++) 
    { 
        for ( $j = 0; $j < $n; $j++) 
        { 
            if ($i == 0) 
                $sum += $a[$i][$j]; 
            else if ($i == $m - 1) 
                $sum += $a[$i][$j]; 
            else if ($j == 0) 
                $sum += $a[$i][$j]; 
            else if ($j == $n - 1) 
                $sum += $a[$i][$j]; 
        } 
    } 
    return $sum; 
} 
  
// Driver code 
$a = array(array(1, 2, 3, 4),  
           array(5, 6, 7, 8),  
           array(1, 2, 3, 4),  
           array(5, 6, 7, 8)); 
             
$sum = getBoundarySum($a, 4, 4); 
echo "Sum of boundary elements is ", $sum; 
  
// This code is contributed by ajit 
?> 

Output:

Sum of boundary elements is 54

This article is contributed by Sarthak Kohli. 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 write comments if you find anything incorrect, or you want to share more information about the topic discussed above.

My Personal Notes

Recommended: Please solve it on “PRACTICE ” first, before moving on to the solution.

C++

Java

Python

C#

PHP

C++

Java

Python

C#

PHP

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