Happy Number

2015.4.22 12:39

Write an algorithm to determine if a number is "happy".

A happy number is a number defined by the following process: Starting with any positive integer, replace the number by the sum of the squares of its digits, and repeat the process until the number equals 1 (where it will stay), or it loops endlessly in a cycle which does not include 1. Those numbers for which this process ends in 1 are happy numbers.

Example: 19 is a happy number

• 12 + 92 = 82
• 82 + 22 = 68
• 62 + 82 = 100
• 12 + 02 + 02 = 1

Solution:

Dull.

Accepted code:

 1 @@ -0,0 +1,36 @@
2 // 1CE, 1AC, dull
3 #include <unordered_set>
4 using namespace std;
5
6 class Solution {
7 public:
8     bool isHappy(int n) {
9         unordered_set<int> us;
10         unordered_set<int>::iterator it;
11
12         while (true) {
13             if (n == 1) {
14                 break;
15             }
16             if (us.find(n) == us.end()) {
17                 us.insert(n);
18             } else {
19                 break;
20             }
21             n = dsum(n);
22         }
23         return n == 1;
24     }
25 private:
26     int dsum(int n) {
27         int s = 0;
28         int d;
29         while (n > 0) {
30             d = n % 10;
31             n /= 10;
32             s += d * d;
33         }
34
35         return s;
36     }
37 };

posted on 2015-04-22 12:43  zhuli19901106  阅读(420)  评论(0编辑  收藏  举报