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LeetCode 387: First Unique Character in a String — Simple Explanation with Carry Logic (Java)

DEV Community·Jerin·27 days ago
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Difficulty : Easy Topics : Hash Table, String, Queue, Counting Platform : Leetcode Problem Statement Given a string s, find the first non-repeating character in it and return its index. If it does not exist, return -1. Problem Statement Simplified Get the index of the first non-repeating character, else return -1. Mistakes and Learning Do not blindly loop thorugh. Do not just delete the duplicates, remove the duplicated character also. Example 1 `Input: s = "leetcode" Output: 0 Explanation: The character 'l' at index 0 is the first character that does not occur at any other index.` Example 2 `Input: s = "loveleetcode" Output: 2` Key Insight Remove all the duplicating characters Then get the first character Get the first character index. If no unique then -1. Algorithm Convert the string to a char array. Intitialize a HashMap to store the character and the repeating counts.…

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