202. Happy Number
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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
思路：
采用set来判断容器中是否有该元素出现过，如果出现过，那么就形成了环状，结果返回false。否则找到快乐数字。返回true。
代码如下：
class Solution {
public:
bool isHappy(int n) {
set myset;
int total = 0;
while(n != 1)
{
while(n)
{
total += (n%10)*(n%10);
n /= 10;
}
if(total == 1)
return true;
if(myset.find(total) != myset.end())
return false;
else
myset.insert(total);
n = total;
total = 0;
}
return true;
}
}; 关于set容器的使用练习。
2016-08-13 13:49:32