<pre name="code" class="java">/**
 * 十进制转三进制，只实现了整数部分
 * @author CaoChenMiao
 *
 */
public class TentoSan {

	private int TtS(int inNum, int index) throws Exception {

		if(inNum < index || index <= 1){
			throw new Exception("不支持的运算");
		}
		String outNum = "";
		
		int maxIndex = getMaxIndex(inNum, index, 0, 0);
		int[] result = new int[maxIndex];
		
		/*方法一：写的时候没有意识到余数就是所需要的值 ╮(╯▽╰)╭
		 * for (int i = 0; i < maxIndex; i++) {
			int pow_ = (int)Math.pow(index, maxIndex-1-i);
			if(inNum - pow_ >= 0){
				result[i] = inNum/pow_;
				inNum -= pow_ * result[i];
			}else if(i != maxIndex-1){
				result[i] = 0;
			}else{
				result[i] = inNum;
			}
		}*/
		//方法二： 简单，便捷
		for (int i = 0; i < maxIndex; i++) {  
            result[i] = inNum % index;  
            inNum = inNum / index;  
        }  
		
		for (int i = 0; i < result.length; i++) {
			outNum += result[i];
		}
		return Integer.parseInt(outNum);
	}

	/**
	 * 计算最高位数
	 * inNum:输入的数字
	 * index：进制数
	 * countNum：累积次数
	 * total：累积和
	 */
	private int getMaxIndex(int inNum, int index, int countNum, int total){
		
		int countTotal = total;
		int count = countNum;
		
		int pow_ = (int)Math.pow(index, ++countTotal);
		while(inNum - pow_ >= 0){
			inNum-=pow_;
			count+=pow_;
			if(inNum - count < 0){
				break;
			}
			return getMaxIndex(inNum, index, count, countTotal);
		}
		return countTotal+1;
	}
	
	
	public static void main(String[] args) throws Exception {
		
		TentoSan ts = new TentoSan();
		System.out.println(ts.TtS(100,3));
		
		//输出结果：10201
		//小结：有返回值的递归函数注意return自身
	}
}