Moderate 判断井字游戏的胜利 @CareerCup

基于要查找的次数来决定是否要预处理。预处理方式按照3进制来做。

另外，检查是否赢了要判断横行，纵列，正反对角线

package Moderate;

/**
 * Design an algorithm to figure out if someone has won in a game of tic-tac-toe.

译文：

设计算法检查某人是否赢得了井字游戏。 
 *
 */
public class S17_2 {

	// 方法一：如果HasWon函数需要被频繁调用
	public static int convertBoardToInt(char[][] board) {
        int factor = 1;
        int sum = 0;
        for (int i = 0; i < board.length; i++) {
                for (int j = 0; j < board[i].length; j++) {
                        int v = 0;
                        switch(board[i][j]){
	                        case 'x':
	                        	v = 1;
	                        	break;
	                        case 'o':
	                        	v = 2;
	                        	break;
                        	default:
                        		v = 0;
                        }
                        
                        sum += v * factor;
                        factor *= 3;
                }
        }
        return sum;
	}
	
	
	// 方法二：如果HasWon函数只被调用一次或很少次
	public static char hasWon(char[][] board){
		int type = 0;
		int N = board.length;
		
		int i, j;
		
		// 对每一行都检查
		for(i=0; i<N; i++){
			if(board[i][0] != ' '){
				for(j=1; j<N; j++){
					if(board[i][j] != board[i][j-1]){
						break;
					}
				}
				if(j == N){
					return board[i][0];
				}
			}
		}
		
		
		// 对每一列都检查
		for(j=0; j<N; j++){
			if(board[0][j] != ' '){
				for(i=1; i<N; i++){
					if(board[i][j] != board[i-1][j]){
						break;
					}
				}
				if(i == N){
					return board[0][j];
				}
			}
		}
		
		// 正对角线检查（左上到右下）
		if(board[0][0] != ' '){
			for(i=1; i<N; i++){
				if(board[i][i] != board[i-1][i-1]){
					break;
				}
			}
			if(i == N){
				return board[0][0];
			}
		}
		
		// 逆对角线检查（左下到右上）
		if(board[N-1][0] != ' '){
			for(i=1; i<N; i++){
				if(board[N-i-1][i] != board[N-i][i-1]){
					break;
				}
			}
			if(i == N){
				return board[N-1][0];
			}
		}
		
		return ' ';
	}



	public static void main(String[] args) {
	        char[][] board = {
	                        {'x', 'x', 'o'},
	                        {' ', 'x', ' '},
	                        {' ', ' ', 'x'}};
	        
	        int v = convertBoardToInt(board);
	        System.out.println(v);
	        
	        char result = hasWon(board);
	        if(result == ' '){
	        	System.out.println("No one won!");
	        }else{
	        	System.out.println(result + " has won");
	        }
	        
	}

}