leetcode 202. Happy Number

<span style="font-family: Arial, Helvetica, sans-serif;">class Solution {</span>

<span style="font-family: Arial, Helvetica, sans-serif;">public:</span>

    bool isHappy(int n) {    unordered_set<int> ss;    while(1)    {    int sum = 0;    while(n)    {    sum += pow((n%10),2);    n /= 10;    }    //cout<<sum<<endl;    if(sum == 1) return true;    if(ss.find(sum) != ss.end())    return false;    ss.insert(sum);    n = sum;    }    }};

使用C++的STL容器unordered_set实现hash存储

unordered_set是C++11 中新添加的容器，是传统的拉链法的哈希实现。对与这类非排序的索引效率更高