Question:
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
Solution:
class Solution { public: bool isHappy(int n) { if(n == 0){ return false; } n = getNum(n); unordered_set<int> mset; while(mset.insert(n).second){ if(n == 1){ return true; } n = getNum(n); } return false; } int getNum(int n){ int res = 0; while(n){ int tmp = n % 10; res += tmp * tmp; n /= 10; } return res; }};總結(jié)：
unordered_set的函數(shù)insert返回值中各個(gè)版本都不一致：
(1) pair
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