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  • Happy Number

    题目描述:

    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

    题目大意:

    编写一个算法判断某个数字是否是“快乐数”。

    快乐数的定义过程如下:从任意一个正整数开始,将原数替换为其每一位的平方和,重复此过程直到数字=1(此时其值将不再变化),或者进入一个不包含1的无限循环。那些以1为过程终止的数字即为“快乐数”。

    例如:19是一个快乐数,演算过程见题目描述。

    解题思路:

    模拟题,循环过程中用set记录每次得到的平方和

    当出现非1的重复平方和时,返回False

    否则,返回True

    C++实现代码:

    class Solution {
    public:
        bool isHappy(int n) {
            set<int> st;
            int sum=0;
            while(true)
            {
                while(n)
                {
                    sum+=(n%10)*(n%10);
                    n/=10;
                }
                if(sum==1)
                    return true;
                else if(st.find(sum)!=st.end())
                    return false;
                else
                    st.insert(sum);
                n=sum;
                sum=0;
            }
        }
    };
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  • 原文地址:https://www.cnblogs.com/wuchanming/p/4469009.html
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