leetcode| Happy Number

Question from https://leetcode.com/problemset/algorithms/    第202题

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

Answer:

class Solution {
public:
    bool isHappy(int n) {
        int *hash = new int[1000];  
          
        for(int i=0;i<1000;i++){  
            hash[i] = 0;  
        }  
        int m = n;  
        bool flag = false;  
        
        while(true){  
            m=getSum(m);  
            if(m==1){  
                flag = true;  
                break;  
            }else if(hash[m]==1||m==n){  
                break;  
            }  
            hash[m] = 1;  
        }  
        return flag;  
    }  
      
    static int getSum(int n){  
        int sum = 0;  
        while(n>0){  
            int t = n%10;  
            sum += t*t;  
            n /= 10;  
        }  
        return sum;  
    } 
};

原文链接：http://blog.youkuaiyun.com/gotobar/article/details/45193515

不知为何C++里的HashTable，Set，Vector等用不了，说是不在可编译范围内，所以找到了这篇博客可以解决问题。

其余code：

1. public class Solution {  
2.     public boolean isHappy(int n) {  
3.         if(n<=0) return false;  
4.         long ln = n;  
5.         Set<Long> set = new HashSet<Long>();  
6.           
7.         while(ln<=Integer.MAX_VALUE) {  
8.             if(set.contains(ln) ) return false; else set.add(ln);  
9.             ln = digitSquare(ln);  
10.             if(ln == 1) return true;  
11.         }  
12.         return false;  
13.     }  
14.       
15.     private long digitSquare(long ln) {  
16.         long sum = 0;  
17.         while(ln!=0) {  
18.             sum += Math.pow(ln%10, 2);  
19.             ln /= 10;  
20.         }  
21.         return sum;  
22.     }  
23. }  

‘Set’ was not declared in this scope   

总是会提示这个错误，不知为何。但代码的解法还是可以的。

原文链接：http://blog.youkuaiyun.com/xudli/article/details/45267247