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  • leetcode Happy Number

    题目连接

    https://leetcode.com/problems/happy-number/  

    Happy Number

    Description

    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


    $1^2 + 9^2 = 82$
    $8^2 + 2^2 = 68$
    $6^2 + 8^2 = 100$
    $1^2 + 0^2 + 0^2 = 1$

    class Solution {
    public:
    	bool isHappy(int n) {
    		if (1 == n) return true;
    		set<int> A;
    		while (true) {
    			int v = 0;
    			do {
    				int i = n % 10;
    				v += i * i;
    			} while (n /= 10);
    			if (1 == v) return true;
    			if (A.find(v) != A.end()) return false;
    			n = v;
    			A.insert(n);
    		}
    	}
    };
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  • 原文地址:https://www.cnblogs.com/GadyPu/p/5028183.html
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