题目

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

题解 Byself

额外写了两个函数
一个用来计算每位数字的平方和
一个用来判断是否=1

class Solution {
public:
    int a=0;
    int temp=0;
    int all=0;
    int num(int n){
        if (n<10) {
            return all+pow(n, 2);
        }
        else{
            all+=pow((n%10),2);
            return num(n/10);
        }
    }
    void isHapp(int n){
        if (n==1) {
            a=1;
        }
        else {
            all=0;
            isHapp(num(n));
        }
    }
    bool isHappy(int n) {
        isHapp(n);
        if (a==1) {
            return true;
        }
        else
            return false;
    }
};

后来看了别人的解法，果然三个可以放在一个里面。。。

优解

class Solution {
public:
    bool isHappy(int n) {
        while (true) {
            int sum=0;
            if (n==1)     return true;
            if(n==4) return false;
            while (n) {
                sum+=(n%10)*(n%10);
                n/=10;
            }
            n=sum;
        }
    }
};

题目
题解 Byself
优解

202. Happy Number

题目

题解 Byself

优解

FEATURED TAGS

FRIENDS