202. Happy Number
Description
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
题意即判断一个数是不是“Happy Num”，即给定数用各位平方和代替，不断重复，最后能否得到1。如果能够得到，就返回true，否则返回false先写一个子函数计算各位平方和，然后再用循环判断是否满足，设定一个上界如果超过我们便认定死循环（这是投机取巧…..），经测试100即可AC。代码如下:
class Solution {
public:
int getSSum(
int n)
{
int rnt =
0;
while (n) {
int m = n %
10;
rnt += m * m;
n /=
10;
}
return rnt;
}
bool isHappy(
int n) {
int ans = getSSum(n);
int times =
0,MAX =
100;
n = ans;
while (ans !=
1 && times++ < MAX) {
ans = getSSum(n);
n = ans;
}
if (ans ==
1)
return true;
else
return false;
}
};
