hdu1128 Self Numbers

Self Numbers

Time Limit: 20000/10000 MS (Java/Others)    Memory Limit: 65536/32768 K (Java/Others)
Total Submission(s): 9356    Accepted Submission(s): 4040

Problem Description

In 1949 the Indian mathematician D.R. Kaprekar discovered a class of numbers called self-numbers. For any positive integer n, define d(n) to be n plus the sum of the digits of n. (The d stands for digitadition, a term coined by Kaprekar.) For example, d(75) = 75 + 7 + 5 = 87. Given any positive integer n as a starting point, you can construct the infinite increasing sequence of integers n, d(n), d(d(n)), d(d(d(n))), .... For example, if you start with 33, the next number is 33 + 3 + 3 = 39, the next is 39 + 3 + 9 = 51, the next is 51 + 5 + 1 = 57, and so you generate the sequence
33, 39, 51, 57, 69, 84, 96, 111, 114, 120, 123, 129, 141, ...

The number n is called a generator of d(n). In the sequence above, 33 is a generator of 39, 39 is a generator of 51, 51 is a generator of 57, and so on. Some numbers have more than one generator: for example, 101 has two generators, 91 and 100. A number with no generators is a self-number. There are thirteen self-numbers less than 100: 1, 3, 5, 7, 9, 20, 31, 42, 53, 64, 75, 86, and 97.


Write a program to output all positive self-numbers less than or equal 1000000 in increasing order, one per line.

Sample Output

1

3

5

7

9

20

31

42

53

64

| | <-- a lot more numbers |

9903

9914

9925

9927

9938

9949

9960

9971

9982

9993

| | |

Source

Mid-Central USA 1998

就是要输出1000000以内所有不能由其它数字组成的数字。

AC代码如下：

//1128
#include<stdio.h>
int f[1000001];
int sum(int a)
{
    int ans=a;
    while(a)
    {
        ans+=a%10;
        a/=10;
    }
return ans;
}
int main()
{
    int i;
    for(i=1;i<1000001;i++)
    {
        if(f[i]==0)
            printf("%d\n",i);
        f[sum(i)]=1;
    }
    return 0;
}