Q solution to LeetCode question 59. can also be used for 54

leetcode59.q

// Define our helper functions

// rotates the box 90 degrees ccw
turn:{[box] flip reverse each box}  

// returns indices of first available nulls in box (top to bottom)
fni:{[box] 1 (where i@)\ first where any each i:null box}  

// fills first nulls in the box with first numbers in the line
ffn:{[box;line;indices] .[box; indices; :; count[indices]#line]}

// Solution - only one i have found so far
// can accept different inputs
//     atomic - n by n matrix (n is the single number passed)
//     list - n by m matrix (n,m are the first,second items of the list respectively)
func:{[x]
  line:1+til (*/)2#x;
  box:(2#x)#0N;
  while[count line; 
    box:turn ffn[box;line] i:fni box;
    line:(count i 1)_line
  ];
  while[1<>.[box;0 0]; box:turn box];
  :box
 }