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263.ugly-number.cpp
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76 lines (62 loc) · 1.3 KB
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// Tag: Math
// Time: O(k)
// Space: O(1)
// Ref: -
// Note: -
// An ugly number is a positive integer whose prime factors are limited to 2, 3, and 5.
// Given an integer n, return true if n is an ugly number.
//
// Example 1:
//
// Input: n = 6
// Output: true
// Explanation: 6 = 2 × 3
//
// Example 2:
//
// Input: n = 1
// Output: true
// Explanation: 1 has no prime factors, therefore all of its prime factors are limited to 2, 3, and 5.
//
// Example 3:
//
// Input: n = 14
// Output: false
// Explanation: 14 is not ugly since it includes the prime factor 7.
//
//
// Constraints:
//
// -231 <= n <= 231 - 1
//
//
class Solution {
public:
bool isUgly(int n) {
if (n < 1) return false;
if (n == 1) return true;
if (n % 2 == 0) {
return isUgly(n / 2);
}
if (n % 3 == 0) {
return isUgly(n / 3);
}
if (n % 5 == 0) {
return isUgly(n / 5);
}
return false;
}
};
class Solution {
public:
bool isUgly(int n) {
if (n < 1) return false;
std::vector<int> primes = {2, 3, 5};
for (auto k : primes) {
while (n % k == 0) {
n = n / k;
}
}
return n == 1;
}
};