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:
use loop to calcuate the square sum until meet one of these two stops:
1. sum is 1, return true
2. sum value got before, which means there is a sum loop and will never goes to 1. return false
public boolean isHappy(int n) { if(n<=0) return false; Set<Long> records = new HashSet<>(); long ln = n; while(ln< Integer.MAX_VALUE){ if(records.contains(ln)) return false; else records.add(ln); ln = getSquareSum(ln); if(ln == 1) return true; } return false; } public long getSquareSum(long n){ long sum = 0; while(n!=0){ sum+= Math.pow(n%10,2); n/=10; } return sum; }
版权声明:本文为博主原创文章,未经博主允许不得转载。
时间: 2024-10-16 06:04:37