Each day I solve several coding challenges and puzzles from Codr's ranked mode. The goal is to reach genius rank, along the way I explain how I solve them. You do not need any programming background to get started, and you will learn a ton of new and interesting things as you go.
function swap(arr, [i, j], [m, n]) { const temp = arr[i][j]; arr[i][j] = arr[m][n]; arr[m][n] = temp; } function rotate(M) { const n = M.length; for (let i = 0; i < n-1; i++) { for (let j = 0; j < n-i; j++) { swap(M, [i, j], [n-j-1, n-i-1]); } } for (let i = 0; i < n/2; i++) { for (let j = 0; j < n; j++) { swap(M, [i, j], [n-i-1, j]); } } } let M = [ [6,5,9], [8,1,5], [3,4,1] ] rotate(M); let A = M[2][1] // A = ? (number) We've encountered this code a couple times before, it's about rotating a matrix by 90 degrees clockwise. By now this should be a piece of cake!
Here's some pseudocode:
M = [ 6 5 9 8 1 5 3 4 1 ] rotate 90° M = [ 3 8 6 4 1 5 1 5 9 ] To find the answer we need to find A = M[2][1] in the rotated matrix, which is 5 (on 3rd row and 2nd column).
By solving these challenges you train yourself to be a better programmer. You'll learn newer and better ways of analyzing, debugging and improving code. As a result you'll be more productive and valuable in business. Get started and become a certified Codr today at https://nevolin.be/codr/
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