263. Ugly Number

Ugly Number

Problem Description

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

Approach) Short Solution

var isUgly = function (n) {
    if(n <= 0) return false

    while (n != 1) {
        if (n % 2 === 0) {
            n /= 2
        } else if (n % 3 === 0) {
            n /= 3
        } else if (n % 5 === 0) {
            n /= 5
        } else {
            return false
        }
    }

    return true
};

Approach) Recursion

/**
 * @param {number} n
 * @return {boolean}
 */
const isUgly = (n) => {
    // Handle all non positive nos
    if(n <= 0) return false;
    // Anything below 5 is ugly
    if(n <= 5) return true;
    
    // Start dividing recursively
    for(const divider of [2, 3, 5]) {
        if(n % divider === 0) {
            return isUgly(n / divider);
        }
    }
    return false;
};




Conclusion

That’s all folks! In this post, we solved LeetCode problem 263. Ugly Number

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