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java - 随机取一个整数,进行拆分,拆分后相加合大于9的话继续拆,直到小于9。

java实现 新手,用字符串拆分怎么实现?
比如100拆成1,0,0 相加大于9的话就继续拆,小于9就输出

PHPzPHPz2891 days ago516

reply all(3)I'll reply

  • 阿神

    阿神2017-04-18 09:08:20

    Just output the number modulo 9


    Proof:

    Suppose the number is:

    $$m=a_na_{n-1}ldots a_0$$

    then

    $$m=sum^n_{i=0}a_itimes10^i$$
    $$=sum^n_{i=0}a_itimes(99dots9+1)$$
    $$equivsum^n_{i=0}a_i (mod 9)$$

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  • PHPz

    PHPz2017-04-18 09:08:20

    This is the original question on leetcode...
    Just take the modulo of 9

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  • 大家讲道理

    大家讲道理2017-04-18 09:08:20

    This uses a direct method and doesn’t feel difficult.

    /**
     * Created by weixuan on 16/6/5.
     */
    public class Test {
    
        // 第一步 to char
    
        public static char[] toChar(Integer data) {
            String value = String.valueOf( data );
            return value.toCharArray();
        }
    
        // 相加
        public static Integer add(char[] data) {
            Integer sum = 0;
            for (char d : data) {
                sum += d - '0';
            }
            return sum;
        }
    
        // 判断是否大于9
        public static Integer isBiggerCore(Integer data) {
            return add( toChar( data ) );
        }
    
        public static Integer isBigger(Integer data) {
            int value = data;
            int temp = isBiggerCore( data );
            while (temp > 9) {
                value = temp;
                temp = isBiggerCore( value );
            }
            return value;
        }
    
        // 987 -> 24
        // 99 -> 18
        // 199 -> 10
        public static void main(String[] args) {
    
            System.out.println(isBigger( 987 ));
        }
    }
    

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