TopCoder SquareDigits

 1 #include <set>
 2 using namespace std;
 3 
 4 class SquareDigits
 5 {
 6     private:
 7         int s(int x);
 8 
 9     public:
10         int smallestResult(int n);
11 };
12 
13 int SquareDigits::s(int x)
14 {
15     int count = 0;
16     while(x >= 10)
17     {
18         int a = x % 10;
19         count += a * a;
20         x = x / 10;
21     }
22 
23     if(x < 10)
24     {
25         count += x * x;
26     }
27 
28     return count;
29 }
30 
31 int SquareDigits::smallestResult(int n)
32 {
33     set<int> se;
34 
35     for(int i=0; ;i++)
36     {
37         int k = i;
38         se.clear();
39         while(1)
40         {
41             k = s(k);
42             if(se.find(k) != se.end())
43             {
44                 break;
45             }
46             se.insert(k);
47             if(k == n)
48             {
49                 break;
50             }
51         }
52 
53         if(k == n && se.find(k) != se.end())
54         {
55             return i;
56         } 
57     }
58 }