LeetCode OJ 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

Credits:

Special thanks to @mithmatt and @ts for adding this problem and creating all test cases.

bool isHappy(int n) {
	int hash[20];
	memset(hash, -1, sizeof(hash));
	while (1) {
		int m = 0;
		while (n) {
			m += (n % 10) * (n % 10);
			n /= 10;
		}
		n = m;
		if (n == 1) return true;
		int p = n % 20;
		while (hash[p] != -1) {
			if (hash[p] == n) return false;
			p++;
			if (p == 20) p = 0;
		}
		hash[p] = n;
	}
}

LeetCode OJ Happy Number

原文：http://blog.csdn.net/u012925008/article/details/45199441