本文主要向大家介绍了C/C++知识点之Self Numbers C语言 UVA640，通过具体的内容向大家展示，希望对大家学习C/C++知识点有所帮助。

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

用离线计算的方法，计算出1000000以内的所有非自我数，将这些数筛掉后再从小到大按序输出。

 1 //UVA 640
 2 #include <stdio.h>
 3 
 4 int a[1000001]; 
 5 
 6 int main(void){
 7     int i,b,c;
 8     for(i=0;i<=1000000;++i){
 9         b=i;c=i;
10         while(c){
11             b+=c%10;
12             c/=10;
13         }
14         a[b]=1;    
15     }
16     for(i=1;i<=1000000;++i)
17         if (!a[i]) printf("%d\n",i);
18     return 0;
19 }

View Code

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