24点计算的源码

public class Point24Utils2 {
	private static String[] opArray = {"+", "-", "*", "-"}; //运算符数组
	private static String[] expArray = new String[11]; //表达式数组
	
	static{
		expArray[0] = "a m1 b m2 c m3 d";
		expArray[1] = "(a m1 b) m2 c m3 d";
		expArray[2] = "(a m1 b m2 c) m3 d";
		expArray[3] = "((a m1 b) m2 c) m3 d";
		expArray[4] = "(a m1 (b m2 c)) m3 d";
		expArray[5] = "a m1 (b m2 c) m3 d";
		expArray[6] = "a m1 (b m2 c m3 d)";
		expArray[7] = "a m1 ((b m2 c) m3 d)";
		expArray[8] = "a m1 (b m2 (c m3 d))";
		expArray[9] = "a m1 b m2(c m3 d)";
		expArray[10] = "(a m1 b) m2 (c m3 d)";
	}
	
	/**
	 * 计算入口方法，返回实际的表达式
	 * @param n 用于计算24点的四个数字组成的数组
	 */
	private static String execute(String[] n){
		String a,b,c,d;	//四个数字
		String m1,m2,m3; //三个运算符
		
		for (int i=0;i<4;i++){
			a = n[i];
			for (int j=0;j<4;j++){
				if ( j == i ) continue; //从未选的三个数字中选择一个数字
				b = n[j];
				for (int x=0;x<4;x++){
					if ( x == i || x == j ) continue;//从未选的两个数字中选择一个数字
					c = n[x];
					for (int y=0;y<4;y++){
						if ( y == i || y == j || y == x ) continue;//从未选的一个数字中选择一个数字
						d = n[y];

						//选择三个运算符
						for (int ta=0;ta<4;ta++){
							m1 = opArray[ta];      
							for (int tb=0;tb<4;tb++){
								m2 = opArray[tb];      
								for (int tc=0;tc<4;tc++){
									m3 = opArray[tc];    
									for (int k=0;k<11;k++){ //11种表达式
										String result = calcalate(expArray[k], a, b, c, d, m1, m2, m3);
										if(result!=null) return result;
									}
								}
							}
						}
					}
				}
			}
		}
		
		return null;
	}
	
	/**
	 * 计算表达式
	 * 
	 * @param exp 待验证的表达式模板
	 * @param a 数字1
	 * @param b 数字2
	 * @param c 数字3
	 * @param d 数字4
	 * @param m1 运算符1
	 * @param m2 运算符2
	 * @param m3 运算符3
	 */
	private static String calcalate(String exp, String a, String b, String c, String d, String m1, String m2, String m3){
		//生成计算表达式
		exp = exp.replaceAll("a", a);
		exp = exp.replaceAll("b", b);
		exp = exp.replaceAll("c", c);
		exp = exp.replaceAll("d", d);
		exp = exp.replaceAll("m1", m1);
		exp = exp.replaceAll("m2", m2);
		exp = exp.replaceAll("m3", m3);
		
		//执行表达式
		FelEngine engine = new FelEngineImpl();
		int result = ((Integer)engine.eval(exp)).intValue();
		
		if(Math.abs(result - 24) < 0.1){
			return exp;
		}else{
			return null;
		}
	}
	
	/**
	 * 取得能算得24的四位数字的集合
	 * @param count 数字组数
	 */
	public static Set<String> genNumbers(int count){
		Set<String> set = new HashSet<String>();
		
		while(true){
			StringBuffer sb = new StringBuffer();
			
			//随机生成四位数字
			String[] n = new String[4];
			for(int i=0;i<n.length;i++){
				String s = String.valueOf(Math.round(Math.floor(Math.random() * 9)) + 1);
				n[i] = s;
				sb.append(s);
			}
			
			//计算
			String result = execute(n);
			if(result!=null && !set.contains(sb.toString())){
				set.add(sb.toString());
				System.out.println(sb.toString() + " : " + result);
			}
			
			if(set.size()==count) break;
		}
		
		return set;
	}
	
	public static void main(String[] args) {
		Set<String> set = genNumbers(5); //随机生成5组能算出24的数字
		System.out.println("ok");
	}
}