标签：ant mit int table tar xpl dig positive eve
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:
Input: 19 Output: true Explanation: 12 + 92 = 82 82 + 22 = 68 62 + 82 = 100 12 + 02 + 02 = 1
Approach #1: C++.
class Solution {
public:
bool isHappy(int n) {
unordered_set<int> s;
s.insert(n);
while (1) {
int summ = 0;
while (n) {
int t = n % 10;
summ += t*t;
n /= 10;
}
if (summ == 1) return true;
if (s.count(summ)) return false;
s.insert(summ);
n = summ;
}
}
};
Approach #2: Java.
class Solution {
public boolean isHappy(int n) {
HashSet<Integer> set = new HashSet<Integer>();
set.add(n);
while (n != 1) {
int result = 0;
while (n != 0) {
result += Math.pow(n % 10, 2);
n /= 10;
}
if (set.contains(result)) {
return false;
}
set.add(result);
n = result;
}
return true;
}
}
Approach #3: Python.
class Solution(object):
def isHappy(self, n):
"""
:type n: int
:rtype: bool
"""
mem = set()
while n != 1:
n = sum([int(i)**2 for i in str(n)])
if n in mem:
return False
else:
mem.add(n)
else:
return True
| Time Submitted | Status | Runtime | Language |
|---|---|---|---|
| a few seconds ago | Accepted | 28 ms | python |
| 2 minutes ago | Accepted | 5 ms | java |
| 8 minutes ago | Accepted | 0 ms | cpp |
标签：ant mit int table tar xpl dig positive eve
原文地址：https://www.cnblogs.com/ruruozhenhao/p/9959997.html
