Recently I was asked to write algorithm to rearrange elements in two-dimensional array in spiral order.
Input array: Output array:
[ 1, 2, 3, 4] [ 1, 2, 3, 4 ]
[ 5, 6, 7, 8] = > [ 8, 12, 11, 10 ]
[ 9, 10, 11, 12] [ 9, 5, 6, 7 ]
I came up with the following solution using JavaScript:
(function(){
var Spiralify = function(matrix){
function isArray(obj){
return Object.prototype.toString.call(obj) === '[object Array]'
}
//Matrix is not specified or not an array
if( !matrix || !isArray(matrix) ) { console.log('Matrix is not an array'); return; }
var rows = matrix.length;
if( rows <= 1 ) return matrix;
//If first element of matrix is not an array, we cant define amount of columns in matrix, so just wrap it in array and return
if(!isArray(matrix[0])) return [matrix];
var cols = matrix[0].length;
//If rows of the matrix are empty arrays, return null
if( cols == 0 ) return matrix;
//If arrays, corresponding to rows, have different amount of elements, return null
if(matrix.some(function(el){ return el.length != cols; })) { console.log('All rows must have equal amount of columns'); return; }
//If we have only one column, just transpond the array and wrap it into another array
if( cols == 1) return [matrix.map(function(i){ return i[0]; })];
function getUpperCorner(r1,c1,r2,c2)
{
for(var i=c1;i<=c2;i++)
tmpArray.push(matrix[r1][i]);
for(var j=r1+1;j<=r2;j++)
tmpArray.push(matrix[j][c2]);
if(r2-r1 > 0)
getLowerCorner(r1+1,c1,r2,c2-1);
}
function getLowerCorner(r1,c1,r2,c2)
{
for(var i=c2;i>=c1;i--)
tmpArray.push(matrix[r2][i]);
for(var j=r2-1;j>=r1;j--)
tmpArray.push(matrix[j][c1]);
if(r2-r1 > 0)
getUpperCorner(r1,c1+1,r2-1,c2);
}
var tmpArray = [];
getUpperCorner(0,0,rows-1,cols-1);
var result = new Array(rows);
for(var i=0;i<rows;i++)
result[i] = tmpArray.splice(0,cols);
return result;
}
var matrix1 = [[1,2,3,4,5],[6,7,8,9,10],[11,12,13,14,15]];
var matrix2 = [[1,2,3,4,5],[6,7,8],[11,12,13,14,15]];
var matrix3 = [[1,2,3,4]];
var matrix4 = [[1],[2],[3],[4],[5],[6]];
var matrix5 = null;
var matrix6 = 1234;
var matrix7 = [];
var matrix8 = [[],[],[]];
var matrix9 = [1,2,3,4];
var matrix10 = 'Hello';
console.log (Spiralify(matrix1));
console.log (Spiralify(matrix2));
console.log (Spiralify(matrix3));
console.log (Spiralify(matrix4));
console.log (Spiralify(matrix5));
console.log (Spiralify(matrix6));
console.log (Spiralify(matrix7));
console.log (Spiralify(matrix8));
console.log (Spiralify(matrix9));
console.log (Spiralify(matrix10));
})(window);
But this solution was a show-stopper. I'm trying to learn from the defeat and would really appreciate some feedback on why this code is unappropriate.