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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.
19 is a happy number
1^2 + 9^2 = 82
8^2 + 2^2 = 68
6^2 + 8^2 = 100
1^2 + 0^2 + 0^2 = 1
public class Solution { /** * @param n an integer * @return true if this is a happy number or false */ boolean[] visited=new boolean[100]; public boolean isHappy(int n) { if (n<visited.length&&visited[n]) return false; if(n<visited.length) { visited[n]=true; } int sum=0; while(n > 0) { int d = n % 10; sum += d * d; n /= 10; } if (sum == 1) return true; return isHappy(sum); } }
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原文地址：http://www.cnblogs.com/kittyamin/p/5055894.html
