![\"\"](\"http:\/\/c-for-dummies.com\/blog\/wp-content\/uploads\/2017\/05\/0527-figure1.png\")
Figure 1. Shifting column one in the magic square doesn’t remove the magic, nor does it change the totals of rows, columns, and diagonals.<\/p><\/div>\n
Can you prove that rotating rows and columns works? Sure! Just add up the rows, columns, and diagonals in your head. Or — better — you can write code that does the work for you.<\/p>\n
The first part of the code is shown below. The magic square is defined as a two-dimensional array. From previous Lessons (here<\/a> and here<\/a>), I explain that a 2D array is bogus, but the notation is useful when coding.<\/p>\n Starting at Line 24, the code moves column 0 to the column 4 position. First, column zero is saved in the Here’s a sample run:<\/p>\n Does the square still work? I added the numbers in my head, and it does, but of course that’s not programming. The preferred method, for this blog, is to run the confirm_magic()<\/em> function on the array. This function was presented in last week’s Lesson<\/a>, but it works only with single-dimension arrays.<\/p>\n This post is a Lesson, not an Exercise, yet I’m going to challenge you to modify the code presented to allow the confirm_magic()<\/em> function to verify the new magic square. You can code the solution on your own, or just wait until next week’s Lesson<\/a> to see what I did. And, no, I’m not using pointers, nor am I folding everything into the main()<\/em> function.<\/p>\n","protected":false},"excerpt":{"rendered":" What happens when you move a row or column in a magic square? Continue reading \r\n#include <stdio.h>\r\n\r\nint main()\r\n{\r\n int grid[5][5] = {\r\n { 25, 13, 1, 19, 7},\r\n { 16, 9, 22, 15, 3},\r\n { 12, 5, 18, 6, 24},\r\n { 8, 21, 14, 2, 20},\r\n { 4, 17, 10, 23, 11}\r\n };\r\n int temp[5];\r\n int row,col;\r\n\r\n\/* display grid *\/<\/span>\r\n puts(\"Original Magic Square\");\r\n for(row=0;row<5;row++)\r\n {\r\n for(col=0;col<5;col++)\r\n printf(\" %2d\",grid[row][col]);\r\n putchar('\\n');\r\n }\r\n\r\n\/* move column 0 to column 4 *\/<\/span>\r\n \/* save column 0 *\/<\/span>\r\n for(row=0;row<5;row++)\r\n temp[row] = grid[row][0];\r\n \/* move columns 1 through 4 *\/<\/span>\r\n for(col=0;col<4;col++)\r\n for(row=0;row<5;row++)\r\n grid[row][col] = grid[row][col+1];\r\n \/* restore column 0 to column 4 *\/<\/span>\r\n for(row=0;row<5;row++)\r\n grid[row][4] = temp[row];\r\n\r\n\/* display grid *\/<\/span>\r\n puts(\"New Magic Square\");\r\n for(row=0;row<5;row++)\r\n {\r\n for(col=0;col<5;col++)\r\n printf(\" %2d\",grid[row][col]);\r\n putchar('\\n');\r\n }\r\n\r\n return(0);\r\n}<\/pre>\ntemp[]<\/code> array. Then the remaining columns, 1 through 4, are shifted to the right. Finally, column zero, stored in the temp[]<\/code> array, is placed at the column 4 position in the grid[][]<\/code> array. I hope you agree that the 2D array notation helps make the code readable.<\/p>\nOriginal Magic Square\r\n 25 13 1 19 7\r\n 16 9 22 15 3\r\n 12 5 18 6 24\r\n 8 21 14 2 20\r\n 4 17 10 23 11\r\nNew Magic Square\r\n 13 1 19 7 25\r\n 9 22 15 3 16\r\n 5 18 6 24 12\r\n 21 14 2 20 8\r\n 17 10 23 11 4<\/code><\/pre>\n