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

 

 

1.把数字各位放入数组，test(int n)方法.

2.计算各位之平方和，getsum(int[] arr)方法.

3.判断结束条件。

 

 

public class Solution {
public boolean isHappy(int n) {

int times=0;
int[] arr = test(n);

int sum = getsum(arr);

while(sum!=1){
int[] ar = test(sum);
sum = getsum(ar);
times++;
if(times>100){//loop times,>100 loops endlessly in a cycle,it works.
return false;
}
}
System.out.println(sum);

return true;
}


//get sum
public int getsum(int[] arr){
int sum = 0;
for(int ii = 0;ii<arr.length;ii++){
sum = sum + arr[ii]*arr[ii];
}
return sum;
}


//get numbers
public int[] test(int n){
String s = String.valueOf(n);
int count = s.length();
int[] arr = new int [count];

for(int i = 0;i<count;i++){
String sc = s.substring(i, i+1);
int is = Integer.parseInt(sc);
arr[i] = is;
//     System.out.println("arr:"+arr[i]);
}
//    System.out.println("--------");

return arr;

}
}

 

 

392 ms.