# Program to reverse the rows in a 2d Array

Given a 2D array arr[][] of size M x N integers where M is the number of rows and N is the number of columns. The task is to reverse every row of the given 2D array.

Example:

```Input: arr[][] =
{ {1, 2, 3},
{4, 5, 6},
{7, 8, 9} }
Output:
3 2 1
6 5 4
9 8 7

Input: arr[][] =
{ {1, 2},
{4, 5},
{7, 8},
{9, 10} }
Output:
2 1
5 4
8 7
10 9
```

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

Approach:

1. For every row in the given 2D array do the following:
• Intialise the start index as 0 and end index as N-1.
• Iterate loop till start index is less than ending index, swap the value at these indexes and update the index as:
```swap(arr[i][start], arr[i][end])
start++;
end--;
```
2. Do the above operation for all the rows in the 2D array.

Below is the implementation of the above approach:

## C++

 `// C++ implementation of the above approach ` ` `  `#include ` `using` `namespace` `std; ` ` `  `const` `int` `M = 3; ` `const` `int` `N = 3; ` ` `  `// A utility function ` `// to swap the two element ` `void` `swap(``int``* a, ``int``* b) ` `{ ` `    ``int` `temp = *a; ` `    ``*a = *b; ` `    ``*b = temp; ` `} ` ` `  `// Function to reverse ` `// the given 2D arr[][] ` `void` `reverseArray(``int` `arr[M][N]) ` `{ ` ` `  `    ``// Traverse each row of arr[][] ` `    ``for` `(``int` `i = 0; i < M; i++) { ` ` `  `        ``// Initialise start and end index ` `        ``int` `start = 0; ` `        ``int` `end = N - 1; ` ` `  `        ``// Till start < end, swap the element ` `        ``// at start and end index ` `        ``while` `(start < end) { ` ` `  `            ``// Swap the element ` `            ``swap(&arr[i][start], ` `                 ``&arr[i][end]); ` ` `  `            ``// Increment start and decrement ` `            ``// end for next pair of swapping ` `            ``start++; ` `            ``end--; ` `        ``} ` `    ``} ` ` `  `    ``// Print the arr[][] after ` `    ``// reversing every row ` `    ``for` `(``int` `i = 0; i < M; i++) { ` `        ``for` `(``int` `j = 0; j < N; j++) { ` `            ``cout << arr[i][j] << ``' '``; ` `        ``} ` `        ``cout << endl; ` `    ``} ` `} ` ` `  `// Driver Code ` `int` `main() ` `{ ` `    ``int` `arr[] = { { 1, 2, 3 }, ` `                     ``{ 4, 5, 6 }, ` `                     ``{ 7, 8, 9 } }; ` ` `  `    ``// Function call ` `    ``reverseArray(arr); ` `    ``return` `0; ` `} `

## Java

 `// Java implementation of the above approach ` `class` `GFG{ ` `  `  `static` `int` `M = ``3``; ` `static` `int` `N = ``3``; ` `  `  ` `  `// Function to reverse ` `// the given 2D arr[][] ` `static` `void` `reverseArray(``int` `arr[][]) ` `{ ` `  `  `    ``// Traverse each row of arr[][] ` `    ``for` `(``int` `i = ``0``; i < M; i++) { ` `  `  `        ``// Initialise start and end index ` `        ``int` `start = ``0``; ` `        ``int` `end = N - ``1``; ` `  `  `        ``// Till start < end, swap the element ` `        ``// at start and end index ` `        ``while` `(start < end) { ` `  `  `            ``// Swap the element ` `            ``int` `temp = arr[i][start]; ` `            ``arr[i][start] = arr[i][end]; ` `            ``arr[i][end] = temp; ` `  `  `            ``// Increment start and decrement ` `            ``// end for next pair of swapping ` `            ``start++; ` `            ``end--; ` `        ``} ` `    ``} ` `  `  `    ``// Print the arr[][] after ` `    ``// reversing every row ` `    ``for` `(``int` `i = ``0``; i < M; i++) { ` `        ``for` `(``int` `j = ``0``; j < N; j++) { ` `            ``System.out.print(arr[i][j] + ``" "``); ` `        ``} ` `        ``System.out.println(); ` `    ``} ` `} ` `  `  `// Driver Code ` `public` `static` `void` `main(String[] args) ` `{ ` `    ``int` `arr[][] = { { ``1``, ``2``, ``3` `}, ` `                     ``{ ``4``, ``5``, ``6` `}, ` `                     ``{ ``7``, ``8``, ``9` `} }; ` `  `  `    ``// Function call ` `    ``reverseArray(arr); ` `} ` `} ` ` `  `// This code is contributed by PrinciRaj1992 `

## Python3

 `# Python3 implementation of the above approach ` `M ``=` `3``;N ``=` `3``; ` ` `  `# Function to reverse ` `# the given 2D arr[][] ` `def` `reverseArray(arr) : ` ` `  `    ``# Traverse each row of arr[][] ` `    ``for` `i ``in` `range``(M) : ` ` `  `        ``# Initialise start and end index ` `        ``start ``=` `0``; ` `        ``end ``=` `N ``-` `1``; ` ` `  `        ``# Till start < end, swap the element ` `        ``# at start and end index ` `        ``while` `(start < end) : ` ` `  `            ``# Swap the element ` `            ``arr[i][start], arr[i][end] ``=` `arr[i][end], arr[i][start]; ` ` `  `            ``# Increment start and decrement ` `            ``# end for next pair of swapping ` `            ``start ``+``=` `1``; ` `            ``end ``-``=` `1``; ` ` `  `    ``# Print the arr[][] after ` `    ``# reversing every row ` `    ``for` `i ``in`  `range``(M) : ` `        ``for` `j ``in` `range``(N) : ` `            ``print``(arr[i][j],end``=` `' '``); ` `     `  `        ``print``(); ` `  `  `# Driver Code ` `if` `__name__ ``=``=`  `"__main__"` `: ` ` `  `    ``arr ``=` `[ [ ``1``, ``2``, ``3` `], ` `            ``[ ``4``, ``5``, ``6` `], ` `            ``[ ``7``, ``8``, ``9` `] ]; ` ` `  `    ``# Function call ` `    ``reverseArray(arr); ` `    `  `# This code is contributed by AnkitRai01 `

## C#

 `// C# implementation of the above approach ` `using` `System; ` ` `  `class` `GFG{ ` `   `  `static` `int` `M = 3; ` `static` `int` `N = 3; ` `   `  `// Function to reverse ` `// the given 2D [,]arr ` `static` `void` `reverseArray(``int` `[,]arr) ` `{ ` `   `  `    ``// Traverse each row of [,]arr ` `    ``for` `(``int` `i = 0; i < M; i++) { ` `   `  `        ``// Initialise start and end index ` `        ``int` `start = 0; ` `        ``int` `end = N - 1; ` `   `  `        ``// Till start < end, swap the element ` `        ``// at start and end index ` `        ``while` `(start < end) { ` `   `  `            ``// Swap the element ` `            ``int` `temp = arr[i,start]; ` `            ``arr[i, start] = arr[i, end]; ` `            ``arr[i, end] = temp; ` `   `  `            ``// Increment start and decrement ` `            ``// end for next pair of swapping ` `            ``start++; ` `            ``end--; ` `        ``} ` `    ``} ` `   `  `    ``// Print the [,]arr after ` `    ``// reversing every row ` `    ``for` `(``int` `i = 0; i < M; i++) { ` `        ``for` `(``int` `j = 0; j < N; j++) { ` `            ``Console.Write(arr[i, j] + ``" "``); ` `        ``} ` `        ``Console.WriteLine(); ` `    ``} ` `} ` `   `  `// Driver Code ` `public` `static` `void` `Main(String[] args) ` `{ ` `    ``int` `[,]arr = { { 1, 2, 3 }, ` `                     ``{ 4, 5, 6 }, ` `                     ``{ 7, 8, 9 } }; ` `   `  `    ``// Function call ` `    ``reverseArray(arr); ` `} ` `} ` ` `  `// This code is contributed by PrinciRaj1992 `

Output:

```3 2 1
6 5 4
9 8 7
```

Don’t stop now and take your learning to the next level. Learn all the important concepts of Data Structures and Algorithms with the help of the most trusted course: DSA Self Paced. Become industry ready at a student-friendly price.

My Personal Notes arrow_drop_up Check out this Author's contributed articles.

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 Improve this article if you find anything incorrect by clicking on the "Improve Article" button below.

Improved By : AnkitRai01, princiraj1992

Article Tags :
Practice Tags :

Be the First to upvote.

Please write to us at contribute@geeksforgeeks.org to report any issue with the above content.