LeetCode 202. Happy Number & 263. Ugly Number
202. 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
由定义即可得到happy number算法，用HashSet来监测循环的产生，如果出现则立即返回false。
public class Solution {
public boolean isHappy(int n) {
// 定义法
int m = n;
Set<Integer> set = new HashSet<Integer>();
while(m != 1) {
if(set.contains(m)) return false;// 出现循环就证明不是
int sum = 0;
set.add(m);
while(m != 0) { // 每次计算各位<span style="color: rgb(51, 51, 51); font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif; font-size: 24px; line-height: 26.3999996185303px;">数字平方相加</span>
sum += Math.pow(m % 10, 2);
m = m /10;
}
m = sum;
}
return true;
}
}
263. Ugly Number
Write a program to check whether a given number is an ugly number.
Ugly numbers are positive numbers whose prime factors only include 2, 3, 5. For example, 6, 8 are ugly while 14 is not ugly since it includes another prime factor 7.
Note that 1 is typically treated as an ugly number.
public class Solution {
public boolean isUgly(int num) {
if(num == 0) return false;
while(num % 2 == 0 || num % 3 == 0 || num % 5 == 0){
if(num % 2 == 0){
num = num / 2;
}else if(num % 3 == 0){
num = num / 3;
}else{
num = num / 5;
}
}
if(num == 1) return true;
return false;
}
}