Write an algorithm to determine if a number n 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.
Return True if n is a happy number, and False if not.
Example:
Input: 19
Output: true
Explanation:
12 + 92 = 82
82 + 22 = 68
62 + 82 = 100
12 + 02 + 02 = 1
C++代碼
class Solution {
int f(int n){
int sum = 0;
while(n){
int digit = n%10;
n/=10;
sum += digit * digit;
}
return sum;
}
public:
bool isHappy(int n) {
for(int rep=0; rep<19; ++rep){
n = f(n);
if(n == 1){
return true;
}
}
return false;
}
};
class Solution{
int f(int n){
int sum = 0;
while(n){
int digit = n % 10;
n /= 10;
sum += digit * digit;
}
return sum;
}
public:
bool isHappy(int n){
unordered_set<int> visited;
while(true){
if(n == 1){
return true;
}
n = f(n);
if(visited.count(n) == 1){
return false;
}
visited.insert(n);
}
}
}