LEETCODE 953:ALIEN ORDER MAP PATTERN: Mastering Alien Dictionary Order: A Comprehensive Guide

Welcome to our detailed walkthrough of LeetCode Problem 953: Verifying an Alien Dictionary. In this video, we will delve deep into understanding the problem, the logic behind the solution, and tips to optimize your approach. Whether you are a beginner or an experienced coder, this guide is designed to help you master this intriguing problem and enhance your problem-solving skills.
Introduction
LeetCode Problem 953, Verifying an Alien Dictionary, is a fascinating problem that tests your understanding of custom orderings and string comparisons. The problem provides an alien language with a specific order of letters and a list of words written in this language. Your task is to determine if the given list of words is sorted according to the alien language order.
Problem Statement
You are given a list of words in an alien language, and the order of the alphabet for this language. You need to check if the words are sorted lexicographically according to the given order. The challenge lies in correctly interpreting the custom order and comparing the words based on this order.
Approach and Explanation
Understanding the Custom Order:
The first step is to comprehend the custom order provided by the alien language. We need to map each character of the alien alphabet to its corresponding position. This will help us quickly compare characters based on their alien language positions.
Mapping the Order:
We create a dictionary that maps each character in the alien alphabet to its index. This dictionary will be used to convert characters in the words to their respective positions for easy comparison.
Comparing Words:
With the custom order mapped, we compare each pair of consecutive words in the list. For each pair, we compare characters one by one based on their positions in the alien language. If we find that a character in the first word has a higher position than the corresponding character in the second word, we know the words are not sorted correctly.
Edge Cases:
Different Lengths: If one word is a prefix of another, the shorter word should come first.
Single Character Words: These should be handled correctly by the character mapping.
Detailed Walkthrough
Let's go through a step-by-step example to solidify our understanding:
Example Input:
Words: ["hello", "leetcode"]
Order: "hlabcdefgijkmnopqrstuvwxyz"
Step-by-Step Process:
Map each character to its position: {'h': 0, 'l': 1, 'a': 2, 'b': 3, ..., 'z': 25}
Compare "hello" and "leetcode":
'h' vs 'l': 'h' comes before 'l' in the custom order, so "hello" should come before "leetcode".
Edge Case Example:
Words: ["apple", "app"]
Order: "abcdefghijklmnopqrstuvwxyz"
"apple" should not come before "app" because "app" is a prefix of "apple".
Tips and Tricks
Efficient Mapping: Use a dictionary for quick look-up times.
Character Comparison: Always convert characters to their respective positions in the custom order before comparing.
Handling Prefixes: Ensure that shorter words come before longer words if the shorter word is a prefix.
Common Mistakes
Ignoring Custom Order: Ensure you are always comparing based on the custom order, not the default lexicographical order.
Not Handling Edge Cases: Always check for edge cases like prefixes and single character words.
Optimization
Time Complexity: The solution involves creating a map which is O(1) and comparing words which is O(n), where n is the total number of characters in all words. This makes the solution efficient and scalable.
Conclusion
Verifying an Alien Dictionary is an excellent problem to enhance your understanding of custom sorting and string manipulation. By following the steps outlined in this video, you can develop a clear and optimized approach to solving this problem. Practice implementing the solution, and don't forget to test with various inputs to ensure your code handles all edge cases effectively.
Thank you for watching this comprehensive guide on LeetCode Problem 953. If you found this video helpful, please like, share, and subscribe to our channel for more coding tutorials and problem-solving strategies. Happy coding!

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