"Vanity Number Search Hackerrank Solutions and Tricks to Ace the Challenge"

Mastering Vanity Number Search on HackerRank

In the dynamic world of competitive programming, platforms like HackerRank offer a plethora of challenges to hone your skills. One such intriguing problem is the 'Vanity Number Search'. This article will guide you through understanding, approaching, and solving this problem, optimizing your search for vanity numbers.

Understanding Vanity Numbers

Vanity numbers are phone numbers that spell out a word or phrase when dialed. For instance, 1-800-FLOWERS is a vanity number for the flower delivery service. In the context of HackerRank, a vanity number is a string of digits that can be rearranged to form a given word.

Problem Statement

The problem on HackerRank presents a list of words and asks you to find out how many of these words can be formed by rearranging the digits of a given phone number. The phone number is represented as a string of digits, and the words are given in a list.

Approach to Solving the Problem

The key to solving this problem is to understand that the frequency of digits in the phone number and the word must match. If the frequency of any digit doesn't match, the word cannot be formed from the phone number. Here's a step-by-step approach:

1. Create a frequency map of digits in the phone number.
2. For each word in the list, create a frequency map of its digits.
3. Compare the frequency maps. If they match, increment a counter.
4. Return the counter at the end.

Implementing the Solution

Here's a simple Python solution following the approach above:

```python def count_vanity_numbers(phone_number, words): phone_freq = [0] * 10 for digit in phone_number: phone_freq[int(digit)] += 1 count = 0 for word in words: word_freq = [0] * 10 for digit in word: word_freq[int(digit)] += 1 if phone_freq == word_freq: count += 1 return count ```

Optimizing the Solution

The above solution has a time complexity of O(n * m * k), where n is the number of words, m is the average length of words, and k is the number of unique digits in the phone number. This can be optimized to O(n * k) by using a single pass to check the frequency of digits in the phone number and the words.

Practice and Learn

HackerRank provides a variety of problems to practice and improve your skills. The 'Vanity Number Search' problem is a great way to understand string manipulation, frequency maps, and optimization techniques. Keep practicing and exploring to become a better coder!