本文介绍了一种算法，用于确定一个数字是否为“幸福数”。幸福数定义为通过替换数字的各位数平方和并重复此过程，最终得到1的数字。以19为例，其过程为：1² + 9² = 82；8² + 2² = 68；6² + 8² = 100；1² + 0² + 0² = 1。
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
Java:
public class Solution {
public boolean isHappy(int n) {
int i = n;
HashSet<Integer> set = new HashSet<Integer>();
while(i != 1)
{
if(set.contains(i))
{
return false;
}
set.add(i);
int k = 0;
while(i>0)
{
k = (i%10)*(i%10) +k;
i = i / 10;
}
i = k;
}
return true;
}
}
public boolean isHappy(int n) {
int i = n;
HashSet<Integer> set = new HashSet<Integer>();
while(i != 1)
{
if(set.contains(i))
{
return false;
}
set.add(i);
int k = 0;
while(i>0)
{
k = (i%10)*(i%10) +k;
i = i / 10;
}
i = k;
}
return true;
}
}
参考了网上使用HashSet，注意循环终止的条件，遇到cycle就返回false
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