05-display-board/day5.js

   1 var fs = require("fs");
   2
   3 const WIDTH = 80;
   4 const HEIGHT = 8;
   5
   6 var initial_grid = new Array(HEIGHT);
   7 for (var i = 0; i < HEIGHT; i++) {
   8   initial_grid[i] = new Array(WIDTH);
   9   for (var j = 0; j < WIDTH; j++) {
  10     initial_grid[i][j] = false;
  11   }
  12 }
  13
  14 function printGrid(g) {
  15     return g.map(function (row) {
  16         return row.map(showCell).join('');
  17     }).join('\n');
  18 }
  19
  20 function showCell(c) {
  21     if (c) {
  22         return '*';
  23     } else {
  24         return ' ';
  25     }
  26 }
  27
  28 // toggle the value of a cell
  29 function toggle(c) {
  30     if (c) {
  31         return false;
  32     } else {
  33         return true;
  34     }
  35 }
  36
  37 // turn a stirng into a command (a three-element array)
  38 function parseCommand(str) {
  39     var command = str.split(' ').slice(-3);
  40     command[1] = Number(command[1]);
  41     command[2] = Number(command[2]);
  42     return command;
  43 }
  44
  45 // implement the instructions
  46 function top(from, to, grid) {
  47     for (var c = from-1; c < to; c++) {
  48         grid[0][c] = toggle(grid[0][c]);
  49     };
  50     return grid;
  51 }
  52
  53 function left(from, to, grid) {
  54     for (var r = from-1; r < to; r++) {
  55         grid[r][0] = toggle(grid[r][0]);
  56     };
  57     return grid;
  58 }
  59
  60 function rotate_column(col, raw_n, grid) {
  61     var n = raw_n % HEIGHT;
  62     var temp_column = new Array(HEIGHT);
  63     for (var i = 0; i < HEIGHT; i++) {
  64         temp_column[i] = grid[i][col-1];
  65     };
  66     var new_col = temp_column.slice(-n).concat(temp_column.slice(0, -n));
  67     for (var i = 0; i < HEIGHT; i++) {
  68         grid[i][col-1] = new_col[i];
  69     };
  70     return grid;
  71 }
  72
  73 function rotate_row(row, raw_n, grid) {
  74     var n = raw_n % WIDTH;
  75     var temp_row = new Array(WIDTH);
  76     for (var i = 0; i < WIDTH; i++) {
  77         temp_row[i] = grid[row-1][i];
  78     };
  79     var new_row = temp_row.slice(-n).concat(temp_row.slice(0, -n));
  80     for (var i = 0; i < WIDTH; i++) {
  81         grid[row-1][i] = new_row[i];
  82     };
  83     return grid;
  84 }
  85
  86
  87 // Dispatch table for execution
  88 var dispatchTable = {'top': top, 'left': left,
  89     'row': rotate_row, 'column': rotate_column};
  90
  91
  92 // Do one command, based on the function stored in the dispatch table
  93 function dispatchCommand(grid, command) {
  94     return dispatchTable[command[0]](command[1], command[2], grid);
  95 }
  96
  97 // Execute all the commands as a fold on the initial grid
  98 function executeCommands(commands, grid) {
  99     return commands.reduce(dispatchCommand, grid);
 100 }
 101
 102
 103 // Merge the lines of the grid into one line, then pick out the true values
 104 function count_pixels(grid) {
 105     return  grid.reduce(
 106                 function (t, l) {return t.concat(l);}
 107             ).filter(
 108                 function (c) {return c;}
 109             ).length
 110 }
 111
 112 var instrs = fs.readFileSync('05-pixels.txt').toString().split('\n');
 113 var instructions = instrs.map(parseCommand);
 114
 115 var final_grid = executeCommands(instructions, initial_grid);
 116
 117 console.log(count_pixels(final_grid));
 118 console.log(printGrid(final_grid));