Snail

October 2013

A snail matrix generator in 133 bytes

s=function(e,c,d,b,f,h,g){c=[[]];d=1;b=h=0;for(f=-1;e;e--){for(g=1;g<2*e;g++)g>e?b+=d:f+=d,c[b]||(c[b]=[]),c[b][f]=++h;d=-d}return c}

See the source code

/**
* Snail
* @param n: the size of the matrix (n*n)
* @return: a 2D array with integers
*/

s = function(n,a,d,x,y,c,i){

  // a is the result matrix
  a = [[]];
  
  // d is the direction: right, bottom = 1; left, top = -1
  d = 1;
  
  // c is the counter value.
  c = 0;
  
  // x and y are the coordinates of the number in the matrix
  x = 0;
  y = -1;

  // Loop while n decrements
  for(; n; n--){

    // The two following loops are merged in the minified code:
    
    // fill n columns
    for(i = 0; i < n; i++){
      
      y += d;
      a[x][y] = ++c;
    }
    
    // fill n-1 lines 
    for(i = 0; i < n - 1; i++){
      
      x += d;
      if(!a[x]){
        a[x] = [];
      }
      a[x][y] = ++c;
    }

    // change direction
    d = -d;
  }
  
  return a;
}

Demo:
Size: Generate