找到最後一個int（1-9）存儲在多個位中（每個int都由4位表示）

Question

我正在研究Tic-Tac-Toe AI，並且希望找到最後一步（在當前轉向之前對手上一步移動）使用遊戲引擎提供的一長串。

每個空間都由一個數字1-9整數表示（我將從中減去1以獲得移動0-8，外加9的移動存儲在0xF中）。

0xE用於表示NULL，但會被我的程序視爲與板外移動相同。

以下是本場比賽的狀態是如何編碼：

Used to encode game State, first 4 bits are first move, second 4 bits second move, (4 * 9 = 36 bits) bits 33-36 are the last Move. Each move is the coordinate singleton + 1, therefore the tictactoe board is recorded as... 
    1 | 2 | 3 
    4 | 5 | 6 
    7 | 8 | 9 

Normal equation for singleton is row*3+col, but you cannot record a state as 0, therefore game state moves are row*3+col + 1, note difference Coordinate singleton is 0..8, board game state position is 1..9; 
1 | 2 | 3 
4 | 5 | 6 
7 | 8 | 9 



The game state 0x159, X first move 9; O move 2 is 5;move 3 X is 1 


X _ _ 
_ O _ 
_ _ 9 



Sets off board set all 4 bits (aka 0xf). 


e.g., 0x12f45, On X's second move (game move 3) 
X picked a Coordinate outside the tictactoe range. 


Duplicate guesses onto occupied square are just saved 


e.g., 0x121 implies X has used position 1 on both his 
first and second move 


Null coordinate usually caused by exception is saved as 0xE 


e.g., 0x1E3; implies on game move 2, O first move, O throw an exception 
most likely causes index array out of bounds 

截至目前，這裏是我如何使用引擎的遊戲狀態找到最後的舉動：

private int LastMoveFinder(final Board brd, int move) 
{ 
    char prevMove = Long.toHexString(brd.getGameState()).charAt(0); 

    if(prevMove == 'f' || prevMove == 'e') 
     return 9; 
    else 
     return Character.getNumericValue(prevMove) - 1; 
} 

但是，我肯定有更快的方式（性能明智的）找到最後一步使用某種位移方法，因爲我們的AI將針對速度（nanoSec /移動）和雙贏損失比率進行測試。

我已經閱讀了有關bitshifting和搜索遍及整個stackoverflow爲我的問題的答案，但沒有任何我試圖實施到我的程序已經工作。

我確定我錯過了一些簡單的東西，但還沒有采取一個涵蓋了偏移和屏蔽的課程，所以我有些失落。

感謝您的幫助。

Answer 1

通過與位掩碼0xf左移4 * moveNumber位，可以得到4位的int。然後，將結果右移4 * moveNumber位以獲得一個int，並將移動邏輯應用於該int。修改後的方法是：

/** 
    Assumes moveNumber is 0 indexed. 
*/ 
private int LastMoveFinder(final Board brd, int moveNumber) 
{ 
    int moveMask = 0xf << (4 * moveNumber); 
    int prevMove = (brd.getGameState() & moveMask) >>> (4 * moveNumber); 

    if (prevMove == 0xf || prevMove == 0xe) { 
     return 9; 
    } else { 
     return prevMove - 1; 
    } 
}