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

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 << "
"; 
    } 
} 
  
// 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; 
} 

/div>

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 "
"; 
    } 
} 
  
// 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

Please write comments if you find anything incorrect, or you want to share more information about the topic discussed above.

C++

Java

Python

C#

PHP

C++

Java

Python

C#

PHP

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