• [LintCode] Happy Number 快乐数


    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

    LeetCode上的原题,请参见我之前的博客Happy Number

    解法一:

    class Solution {
    public:
        /**
         * @param n an integer
         * @return true if this is a happy number or false
         */
        bool isHappy(int n) {
            set<int> s;
            while (n != 1) {
                int t = 0;
                while (n) {
                    t += (n % 10) * (n % 10);
                    n /= 10;
                }
                n = t;
                if (s.count(n)) break;
                else s.insert(n);
            }
            return n == 1;
        }
    };

    解法二:

    class Solution {
    public:
        /**
         * @param n an integer
         * @return true if this is a happy number or false
         */
        bool isHappy(int n) {
            while (n != 1 && n != 4) {
                int t = 0;
                while (n) {
                    t += (n % 10) * (n % 10);
                    n /= 10;
                }
                n = t;
            }
            return n == 1;
        }
    };

     

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  • 原文地址:https://www.cnblogs.com/grandyang/p/5560036.html
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