leetcode 202 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

我的解决方案：

// happy number.cpp : Defines the entry point for the console application.
//

#include "stdafx.h"
#include <iostream>
#include <set>
using namespace std;


  bool isHappy(int n)
    {
        int split = 0;
        int sum = 0;
        
        set<int> myset;
        set<int>::iterator it;
        
        while(sum != 1)
        {
            do
            {
                split = n % 10;
                n = n / 10;
                sum = split* split + sum;
            }
			while(n>0);
                
            if(sum==1)
            {
                break;
            }
            else
            {
                    
                it=myset.find(sum);
				if(it!=myset.end())
                {
                    return false;
                }
                myset.insert(sum);
				n = sum;
				sum = 0;

            }

        }
        
        return true;
    }
int _tmain(int argc, _TCHAR* argv[])
{

	isHappy(19);
	return 0;
}

最短的一个代码，用了些数论的知识吧：

https://leetcode.com/discuss/33014/4ms-5-line-c-code

bool isHappy(int n) {
    while(n>6){
        int next = 0;
        while(n){next+=(n%10)*(n%10); n/=10;}
        n = next;
    }
    return n==1;
}

两个python代码：



 def isHappy(self, n):
    return self.isHappyHelper(n, {})

def isHappyHelper(self, n, prev):
    if n == 1:
        return True
    elif n not in prev:
        prev[n] = 1
    else:
        return False

    new = 0
    for char in str(n):
        new += int(char)**2

    return self.isHappyHelper(new, prev)

class Solution:
# @param {integer} n
# @return {boolean}
def isHappy(self, n):
    table = []
    n = self.convert(n)
    while n != 1:
        if n in table:
            return False
        else:
            table.append(n)
            n = self.convert(n)
    return True

# @param {integer} n
# @return {integer} sum of digits
def convert(self, n):
    res = 0
    while n > 0:
        temp = n % 10
        res += temp * temp
        n = n // 10
    return res