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@fabslab fabslab/spiral.js
Last active Apr 5, 2016

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/**
* Returns a string concatenation of the elements of a matrix (2d array) in "spiral" order.
* @param {[[]]} matrix - the 2d array
* @param {string} [separator] - optional separator to use between values in string, defaults to ", "
* @returns {string}
*/
function spiralMatrix(matrix, separator) {
if (matrix.length === 0 || matrix[0].length === 0) {
return "";
}
var firstRow = 0;
var firstColumn = 0;
var lastRow = matrix.length - 1;
var lastColumn = matrix[0].length - 1;
return spiralMatrixRecursive(matrix, firstRow, lastRow, firstColumn, lastColumn).join(separator || ", ");
}
function spiralMatrixRecursive(matrix, topRow, bottomRow, leftColumn, rightColumn) {
var result = [];
if (topRow > bottomRow || leftColumn > rightColumn) {
return result;
}
var currentRow;
var currentColumn;
// loop through top row
for (currentColumn = leftColumn; currentColumn <= rightColumn; currentColumn++) {
result.push(matrix[topRow][currentColumn]);
}
// loop through rest of right column
for (currentRow = topRow + 1; currentRow <= bottomRow; currentRow++) {
result.push(matrix[currentRow][rightColumn]);
}
if (topRow !== bottomRow) {
// loop through rest of bottom row
for (currentColumn = rightColumn - 1; currentColumn >= leftColumn; currentColumn--) {
result.push(matrix[bottomRow][currentColumn]);
}
}
if (leftColumn !== rightColumn) {
// loop through rest of left column (stop before top row as already done)
for (currentRow = bottomRow - 1; currentRow > topRow; currentRow--) {
result.push(matrix[currentRow][leftColumn]);
}
}
return result.concat(spiralMatrixRecursive(matrix, topRow + 1, bottomRow - 1, leftColumn + 1, rightColumn - 1));
}
/**
* Generates a matrix (2d array) with the given number of rows and columns,
* containing random numbers between 1 and 10.
* @param rows - number of rows
* @param columns - number of columns
* @returns {Array} - the matrix
*/
function generateMatrix(rows, columns) {
var matrix = [];
for (var i = 0; i < rows; i++) {
matrix.push([]);
for (var j = 0; j < columns; j++) {
matrix[i][j] = Math.floor((Math.random() * 10) + 1);
}
}
return matrix;
}
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