LeetCode-Happy Number-解題報告

原題鏈接 https://leetcode.com/problems/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

模擬法，模擬題中描述的方法即可。使用hash記錄那個數字訪問過沒有就行了。

class Solution {
public:
    bool isHappy(int n) {
		unordered_map<int, bool>vis;
		while (n != 1)
		{
			vis[n] = true;
			n = getSs(n);
			if (vis[n])return false;
		}
		return true;
	}
	int getSs(int x)
	{
		int sum = 0;
		while (x)
		{
			int t = x % 10;
			sum += t*t;
			x /= 10;
		}
		return sum;
	}
};