leetcode_c++：哈希： Happy Number(202)

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

算法

O（N）

hash的方法

//
//  main.cpp
//  CplusplusTest
//
//  Created by mijian on 16/7/1.
//  Copyright © 2016年 mijian. All rights reserved.
//

#include <iostream>
#include <string>
#include <vector>
#include <map>
#include <limits.h>
#include <unordered_map>
#include <sstream>
#include<unordered_set>

using  namespace std;

class Solution {
public:
bool isHappy(int n) {
unordered_set<int>  vis;

while(vis.find(n)==vis.end()){
vis.insert(n);
int tmp=0;
while(n){
tmp+=(n%10)*(n%10);
n/=10;
}

n = tmp;
if(n==1)
return true;
}

return false;

}
};

int main(){
Solution s;
int n;
for(n=0;n<10000;++n){
if(s.isHappy(n))
cout<<n<<", ";
}

return 0;
}