spiral-matrix-ii.js

// Given a positive integer n, generate a square matrix filled with elements from 1 to n2 in spiral order.
//
// Example:
//
//
// Input: 3
// Output:
// [
//  [ 1, 2, 3 ],
//  [ 8, 9, 4 ],
//  [ 7, 6, 5 ]
// ]
//
//


/**
 * @param {number} n
 * @return {number[][]}
 */
var generateMatrix = function(n) {
     var result = new Array(n);
     for (var i = 0;i < n;++i) {
         result[i] = new Array(n);
     }
     i = 1;
     var x = 0, y = 0, dir = 0;
     var nextPos = function(x, y) {
         while (true) {
             var newX = x, newY = y;
             switch (dir) {
                 case 0: //right
                 ++newX; break;
                 case 1: //down
                 ++newY; break;
                 case 2: //left
                 --newX; break;
                 case 3: //up
                 --newY; break;
             }
             if (newX < 0 || newX >= n || newY < 0 || newY >= n || result[newY][newX]) {
                 dir = (dir + 1) % 4;
             } else {
                 return [newX, newY];
             }
         }
     };
     while (i <= n * n) {
         result[y][x] = i;
         if (i < n * n) {
             var pos = nextPos(x, y);
             x = pos[0];
             y = pos[1];
         }
         ++i;
     }
     return result;
};