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@Determinant

Determinant/Game2048.java

Last active August 9, 2016 01:32
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  1. Ted Yin revised this gist Jul 27, 2015. 1 changed file with 13 additions and 9 deletions.
    22 changes: 13 additions & 9 deletions Game2048.java
    View file
    Original file line number Diff line number Diff line change
    @@ -30,18 +30,22 @@ public int moveLeft(int[][] b, int i) {
    }
    else
    {
    b[i][h += (b[i][h] != 0 ? 1 : 0)] = b[i][j];
    /* different value, so that the value x at h already has its final value:
    if x == 0
    <0>, ..., y --> <y>, ...
    else
    <x>, 0, ..., y --> x, <y>, ... */
    if (h != j)
    /* different value, so that the value x at h already has its final value */
    if (b[i][h] == 0)
    {
    moveMade = true;
    b[i][h] = b[i][j]; /* <0>, ..., y --> <y>, ... */
    b[i][j] = 0;
    }
    /* if h == j, nothing is moved */
    else
    {
    b[i][++h] = b[i][j]; /* <x>, 0, ..., y --> x, <y>, ... */
    if (h != j)
    {
    moveMade = true;
    b[i][j] = 0;
    }
    /* if h == j, nothing is moved */
    }
    }
    }
    return moveMade ? bonus: -1;
  2. Ted Yin created this gist Jul 27, 2015.
    59 changes: 59 additions & 0 deletions Game2048.java
    View file
    Original file line number Diff line number Diff line change
    @@ -0,0 +1,59 @@
    /*
    * Author: Ted Yin (Maofan Yin) <[email protected]>
    * Description: Implementation for performing a move in direction left in 2048 game
    */

    class Game2048 {
    public int moveLeft(int[][] b, int i) {
    int bonus = 0;
    int h = 0; /* b[i][0..h-1] has its final value and cannot be changed
    again (exactly the same definition in your hint) */
    boolean moveMade = false;
    /* loop invariant:
    * +-------------row: b[i]----------------------+
    * |###########<x>00000000??????????????????????|
    * +0-----------h---------j---------------------+
    * "#": has their final values and cannot be changed
    * "<x>": the next value to be finalized (still mergable)
    * "0": blanks
    * "?": not discovered
    */
    for (int j = 1; j < b[i].length; j++)
    {
    if (b[i][j] == 0) continue; /* skip blanks */
    if (b[i][j] == b[i][h])
    {
    bonus += (b[i][h++] += b[i][j]); /* merge with the previous same value:
    <x>, z, ..., x --> (x + x), <z>, ... */
    moveMade = true;
    b[i][j] = 0;
    }
    else
    {
    b[i][h += (b[i][h] != 0 ? 1 : 0)] = b[i][j];
    /* different value, so that the value x at h already has its final value:
    if x == 0
    <0>, ..., y --> <y>, ...
    else
    <x>, 0, ..., y --> x, <y>, ... */
    if (h != j)
    {
    moveMade = true;
    b[i][j] = 0;
    }
    /* if h == j, nothing is moved */
    }
    }
    return moveMade ? bonus: -1;
    }

    public static void main(String [] args) {
    /* A simple test of written routine */
    Game2048 game = new Game2048();
    int[][] grid = new int[][]{new int[] {2, 4, 4, 8, 0, 8, 8}};
    System.out.printf("%d:", game.moveLeft(grid, 0));
    for (int j = 0; j < grid[0].length; j++)
    System.out.printf(" %d", grid[0][j]);
    System.out.printf("\n");
    }
    }