Swap Rows and Columns of 2D Array in C#
Author: Markus Weller IN: Array, C#, Column, Row Comments: 0
Background
The following methods seem to be very simple, but there are many unanswered questions in Q&A websites like “Stackoverflow” of people who are searching for a simple and quick way to swap entire columns or rows of 2D arrays.That’s why I decided to publish my methods to do this.
I needed those methods because I often had to swap entire parts of arrays while trying to solve the “Einstein Riddle” in a C# Program.
How the Methods work
The source code should be self explaining but that’s how it is working in general:
- Clone the Array
- Check for every X value of the array if it matches with the A.
- If it matches replace it with the X value of B of the original array.
- Check for every X value of the array if it matches with the B.
- If it matches replace it with the X value of A of the original array.
Swapping columns works in the same way, but you have to compare and replace the Y values.
How the Methods are used
Parameters are a rectangular 2D Array and the index of the rows/columns which should get swapped.
The indexes may not be out of the Bounds of the Array, otherwise a “IndexOutOfRangeException” is thrown and the array will not change at all. If you remove the following codes no exceptions will be thrown but the array still doesn’t change at all if you pass bad values for A or B.
“throw new IndexOutOfRangeException();”
The methods will return an array where the rows / columns are swapped.
Swap 2 Rows
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/// <summary> /// Swaps two rows of a two dimensional array of strings. /// </summary> /// <param name="array">The Array which should be changed</param> /// <param name="a">this row will get swaped with the row b</param> /// <param name="b">this row will get swaped with the row a</param> /// <returns>The input array, but a and b are swaped</returns> static string[,] swapRows(string[,] array, int a, int b) { //clone the array string[,] clone = (string[,])array.Clone(); //fill A of the clone with B of the original for (int i = 0; i <= clone.GetLength(0) - 1; i++) { if (i == a) { for (int j = 0; j <= clone.GetLength(1) - 1; j++) { if (b <= clone.GetLength(0) - 1 && b >= 0) { clone[i, j] = array[b, j]; } else { throw new IndexOutOfRangeException(); } } } } //fill B of the clone with A of the original for (int i = 0; i <= clone.GetLength(0) - 1; i++) { if (i == b) { for (int j = 0; j <= clone.GetLength(1) - 1; j++) { if (a <= clone.GetLength(0) - 1 && a >= 0) { clone[i, j] = array[a, j]; } else { throw new IndexOutOfRangeException(); } } } } return clone; } |
Swap 2 Columns
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/// <summary> /// Swaps two columns of a two dimensional array of strings. /// </summary> /// <param name="array">The Array which should be changed</param> /// <param name="a">this column will get swaped with the row b</param> /// <param name="b">this column will get swaped with the row a</param> /// <returns>The input array, but a and b are swaped</returns> static string[,] swapColumns(string[,] array, int a, int b) { //clone the array string[,] clone = (string[,])array.Clone(); //fill A of the clone with B of the original for (int i = 0; i <= clone.GetLength(0) - 1; i++) { for (int j = 0; j <= clone.GetLength(1) - 1; j++) { if (j == a) { if (b <= clone.GetLength(1) - 1 && b >= 0) { clone[i, j] = array[i, b]; } else { throw new IndexOutOfRangeException(); } } } } //fill B of the clone with A of the original for (int i = 0; i <= clone.GetLength(0) - 1; i++) { for (int j = 0; j <= clone.GetLength(1) - 1; j++) { if (j == b) { if (a <= clone.GetLength(1) - 1 && a >= 0) { clone[i, j] = array[i, a]; } else { throw new IndexOutOfRangeException(); } } } } return clone; } |
07-19
2012
