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Print a matrix in alternate manner (left to right then right to left)
• Difficulty Level : Basic
• Last Updated : 02 Jan, 2019

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[] = {{1, 2}
{2, 3}};
Output : 1  2  3  2

Input :arr[] = { { 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``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=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

 `= 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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