Print a matrix in alternate manner (left to right then right to left)

Given a 2D array, the task is to print the 2D in alternate manner (First row from left to right, then from right to left, and so on).

Examples:

Input : arr[][2] = {{1, 2}
                    {2, 3}}; 
Output : 1  2  3  2 
 
Input :arr[][3] = { { 7 , 2 , 3 },
                    { 2 , 3 , 4 },
                    { 5 , 6 ,  1 }}; 
Output : 7  2   3  4  3  2  5  6  1

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

The solution of this problem is that run two loops and and print row in left to right and right to left manners. We maintain a flag to see if current row should be printed from left to right or right to left. We toggle the flag after every iteration.

C++

// C++ program to print matrix in alternate manner 
#include<bits/stdc++.h> 
using namespace std; 
#define R 3 
#define C 3 
  
// Function for print matrix in alternate manner 
void convert(int arr[R][C]) 
{ 
    bool leftToRight = true; 
    for (int i=0; i<R; i++) 
    { 
        if (leftToRight) 
        { 
            for (int j=0; j<C; j++) 
                printf("%d ", arr[i][j]); 
        } 
        else
        { 
            for (int j=C-1; j>=0; j--) 
                printf("%d ",arr[i][j]); 
        } 
  
        leftToRight = !leftToRight; 
    } 
} 
  
// Driver code 
int main() 
{ 
    int arr[][C] = 
    { 
        { 1 , 2 , 3 }, 
        { 3 , 2 , 1 }, 
        { 4 , 5 , 6 }, 
    }; 
  
    convert(arr); 
    return 0; 
} 

Java

//Java program to print matrix in alternate manner  
class GFG { 
  
    static final int R = 3; 
    static final int C = 3; 
  
// Function for print matrix in alternate manner  
    static void convert(int arr[][]) { 
        boolean leftToRight = true; 
        for (int i = 0; i < R; i++) { 
            if (leftToRight) { 
                for (int j = 0; j < C; j++) { 
                    System.out.printf("%d ", arr[i][j]); 
                } 
            } else { 
                for (int j = C - 1; j >= 0; j--) { 
                    System.out.printf("%d ", arr[i][j]); 
                } 
            } 
  
            leftToRight = !leftToRight; 
        } 
    } 
  
// Driver code  
    static public void main(String[] args) { 
        int arr[][] 
                = { 
                    {1, 2, 3}, 
                    {3, 2, 1}, 
                    {4, 5, 6},}; 
  
        convert(arr); 
    } 
} 
  
// This code is contributed by Rajput-Ji 

Python 3

# Python 3 program to print matrix  
# in alternate manner 
R = 3
C = 3
  
# Function for print matrix 
# in alternate manner 
def convert(arr): 
  
    leftToRight = True
    for i in range(R): 
        if (leftToRight): 
            for j in range(C): 
                print(arr[i][j], end = " ") 
      
        else: 
            for j in range(C - 1, -1, -1): 
                print(arr[i][j], end = " ") 
  
        leftToRight = not leftToRight 
  
# Driver code 
if __name__ == "__main__": 
    arr =[[ 1 , 2 , 3 ], 
          [ 3 , 2 , 1 ], 
          [ 4 , 5 , 6 ]] 
  
    convert(arr) 
  
# This code is contributed  
# by ChitraNayal 

C#

      
//C# program to print matrix in alternate manner 
using System; 
public class GFG { 
   
    static readonly int R = 3; 
    static readonly int C = 3; 
   
// Function for print matrix in alternate manner  
    static void convert(int [,]arr) { 
        bool leftToRight = true; 
        for (int i = 0; i < R; i++) { 
            if (leftToRight) { 
                for (int j = 0; j < C; j++) { 
                    Console.Write(arr[i,j]+" "); 
                } 
            } else { 
                for (int j = C - 1; j >= 0; j--) { 
                    Console.Write(arr[i,j]+" "); 
                } 
            } 
   
            leftToRight = !leftToRight; 
        } 
    } 
   
// Driver code  
    static public void Main() { 
        int [,]arr 
                = { 
                    {1, 2, 3}, 
                    {3, 2, 1}, 
                    {4, 5, 6},}; 
   
        convert(arr); 
    } 
} 
   
// This code is contributed by Rajput-Ji 

PHP

<?php 
// PHP program to print matrix  
// in alternate manner 
$R = 3; 
$C = 3; 
  
// Function for print matrix 
// in alternate manner 
function convert($arr) 
{ 
    global $R; 
    global $C; 
    $leftToRight = true; 
    for ($i = 0; $i < $R; $i++) 
    { 
        if ($leftToRight) 
        { 
            for ($j = 0; $j < $C; $j++) 
                echo $arr[$i][$j], " "; 
        } 
        else
        { 
            for ($j = $C - 1; $j >= 0; $j--) 
                echo $arr[$i][$j], " "; 
        } 
  
        $leftToRight = !$leftToRight; 
    } 
} 
  
// Driver code 
$arr = array(array(1 , 2 , 3 ), 
             array(3 , 2 , 1 ), 
             array(4 , 5 , 6 )); 
  
convert($arr); 
  
// This code is contributed by ajit 
?> 

Output:

1 2 3 1 2 3 4 5 6

Time Complexity : O(R*C)
Space Complexity : O(1)

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My Personal Notes

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

C++

Java

Python 3

C#

PHP

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