202. Happy Number

2019-11-08 02:19:52

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題目

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 Credits: Special thanks to @mithmatt and @ts for adding this problem and creating all test cases.

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思路

循環求happyNum，退出條件是為1返回true，數字重復形成循環則返回false

代碼

class Solution {public: int getHappyNum(int num) { int result = 0; while(num) { result += pow(num%10,2); num /= 10; } return result; } bool isHappy(int n) { if(n <= 0) { return false; } vector<int> numFlag; numFlag.push_back(n); while(n) { n = getHappyNum(n); if(n == 1) { return true; } //形成循環了 if(find(numFlag.begin(),numFlag.end(),n) != numFlag.end()) { return false; } numFlag.push_back(n); } return false; }};

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