LeetCode: 263. Ugly Number
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LeetCode: 263. Ugly Number
题目描述
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.
Example 1:
Input: 6
Output: true
Explanation: 6 = 2 × 3
Example 2:
Input: 8
Output: true
Explanation: 8 = 2 × 2 × 2
Example 3:
Input: 14
Output: false
Explanation: 14 is not ugly since it includes another prime factor 7.
Note:
-
1 is typically treated as an ugly number. - Input is within the 32-bit signed integer range:
[−2^31, 2^31 − 1].
解题思路 —— 递归求解
如果能 num 被 2, 3, 5, 整除， 则 isUgly(num) == isUgly(num/x)，其中 x = 2 或 3 或 5
AC 代码
class Solution {
public:
bool isUgly(int num) {
if(num == 1)
{
return true;
}
else if(num == 0)
{
return false;
}
else if(num % 2 == 0)
{
return isUgly(num/2);
}
else if(num % 5 == 0)
{
return isUgly(num/5);
}
else if(num % 3 == 0)
{
return isUgly(num/3);
}
else
{
return false;
}
}
};
