202. Happy Number

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：

classSolution{public:boolisHappy(intn){set<int>myset;inttotal=0;while(n!=1){while(n){total+=(n%10)*(n%10);n/=10;}if(total==1)returntrue;if(myset.find(total)!=myset.end())returnfalse;elsemyset.insert(total);n=total;total=0;}returntrue;}};

关于set容器的使用练习。

2016-08-13 13:49:32