/**
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.
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.
Return true if n is a happy number, and false if not.
Example 1:
Input: n = 19
Output: true
Explanation:
1² + 9² = 82
8² + 2² = 68
6² + 8² = 100
1² + 0² + 0² = 1
Example 2:
Input: n = 2
Output: false
Constraints:
1 <= n <= 2³¹ - 1
Related Topics哈希表 | 数学 | 双指针
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*/
//leetcode submit region begin(Prohibit modification and deletion)
class Solution {
public boolean isHappy(int n) {
Set<Integer> sumSet = new HashSet();
while (!sumSet.contains(n)) {
sumSet.add(n);
int newn = 0;
while (n > 0) {
int single = n % 10;
newn += (single * single);
n = n / 10;
}
if (newn == 1) {
return true;
}
n = newn;
}
return false;
}
}
//leetcode submit region end(Prohibit modification and deletion)
