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Day 26 - Array Series Part 9: Spiral Matrix Generation and Matrix Spiral Copy

Question 1 - Spiral Matrix Generation (1D to 2D)

Question 1 – Write a function that accepts an integer N and generates an NxN spiral matrix

Example

input: N=2 output: [ [1, 2], [4, 3] ] input: N=3 output: [ [1, 2, 3], [8, 9, 4], [7, 6, 5] ]

Question 2 - Matrix Spiral Copy (2D to 1D)

Given a 2D array (matrix) inputMatrix of integers, create a function spiralCopy that copies inputMatrix’s values into a 1D array in a spiral order, clockwise. Your function then should return that array.

Example

input: inputMatrix = [ [1, 2, 3, 4, 5], [6, 7, 8, 9, 10], [11, 12, 13, 14, 15], [16, 17, 18, 19, 20] ] output: [1, 2, 3, 4, 5, 10, 15, 20, 19, 18, 17, 16, 11, 6, 7, 8, 9, 14, 13, 12]

ques

Solution to problem 1 - Spiral Matrix Generation

JavaScript Implementation

Solution

/** * Spiral Matrix Generation * @author MadhavBahl * @date 24/01/2019 */ function spiralGeneration (num) { let spiral = [], topRow = 0, btmRow = num-1, leftCol = 0, rightCol = num-1, count = 1; // Initialize the spiral matrix with zeros for (let i=0; i<num; i++) { let thisRow = []; for (let j=0; j<num; j++) thisRow.push (0); spiral.push (thisRow); } // Populate the matrix while ((topRow<=btmRow) && (leftCol<=rightCol)) { // Populate the top row for (let i=leftCol; i<=rightCol; i++) spiral[topRow][i] = count++; topRow++; // Populate the right column for (let i=topRow; i<=btmRow; i++) spiral[i][rightCol] = count++; rightCol--; // Populate the bottom row IF toprow has not become greater than bottom row if (topRow <= btmRow) { for (let i=rightCol; i>=leftCol; i--) spiral[btmRow][i] = count++; btmRow--; } // Populate the left column IF rightCol has not become less than left Col if (rightCol >= leftCol) { for (let i=btmRow; i>=topRow; i--) spiral[i][leftCol] = count++; leftCol++; } } // Print the result console.log (spiral); return spiral; } spiralGeneration (2); spiralGeneration (3); spiralGeneration (4); spiralGeneration (5);

Solution to problem 2 - Matrix Spiral Copy

JavaScript Implementation

Solution

function spiralCopy(inputMatrix) { // your code goes here let outputArray = [], numRow = inputMatrix.length, numCol = inputMatrix[0].length; let topRow = 0, btmRow = numRow - 1, leftCol = 0, rightCol = numCol - 1; while ((topRow <= btmRow) && (leftCol <= rightCol)) { for (let i=leftCol; i<=rightCol; i++) { outputArray.push(inputMatrix[topRow][i]); } topRow++; for (let i=topRow; i<=btmRow; i++) { outputArray.push(inputMatrix[i][rightCol]); } rightCol--; if (topRow <= btmRow) { for (let i=rightCol; i>=leftCol; i--) { outputArray.push(inputMatrix[btmRow][i]); } btmRow--; } if (leftCol <= rightCol) { for (let i=btmRow; i>=topRow; i--) { outputArray.push(inputMatrix[i][leftCol]); } leftCol++; } } return outputArray; } console.log(spiralCopy([ [1, 2, 3, 4], [6, 7, 8, 9], [11, 12, 13, 14], [16, 17, 18, 19] ])); // Should print [ 1, 2, 3, 4, 9, 14, 19, 18, 17, 16, 11, 6, 7, 8, 13, 12 ] console.log(spiralCopy([ [1, 2, 3, 4, 5], [6, 7, 8, 9, 10], [11, 12, 13, 14, 15], [16, 17, 18, 19, 20] ])); // Should print [ 1, 2, 3, 4, 5, 10, 15, 20, 19, 18, 17, 16, 11, 6, 7, 8, 9, 14, 13, 12 ]