22
04/2015
[LeetCode] Happy Number
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
Credits:
Special thanks to @mithmatt and @ts for adding this problem and creating all test cases.
解题思路：
模拟法即可。用一个set记录所有计算过的n，若出现重复（循环），返回false，若n为1，返回true;
class Solution {
public:
bool isHappy(int n) {
if(n<=0){
return false;
}
set<int> checkedNumber;
while(n!=1){
checkedNumber.insert(n);
int tempN=0;
while(n!=0){
int num=n%10;
n=n/10;
tempN+=num*num;
}
n=tempN;
if(checkedNumber.find(n)!=checkedNumber.end()){
return false;
}
}
return true;
}
};转载请注明：康瑞部落 » [LeetCode] Happy Number
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