Find Length of Longest Substring without Repeating Characters in JavaScript | Learn JavaScript

Find length of longest substring without repeating characters in javascript. How to write a javascript function to find the length of the longest substring without repeating characters? What is a substring? A substring is a sequence of characters within a string. For example: 'web' is a substring of the string 'webstylepress'. In 'webstylepress', length of longest substring without repeating characters is 8. It's 'bstylepr'. Because from left or right e is a repeating character. But if we look from b to r, this makes a substring without repeating characters and it has 8 characters.

So write a javascript function to find the length of the longest substring without repeating characters. It is a common javascript interview question.

Let's define a function called "longestSubstring" that takes in a string as an argument. Initialize variables for the maximum length of the substring (maxLen) and the current length of the substring (currLen) to 0. Initializes an empty object called "charMap" and a variable "start" to 0.

We will use a 'Sliding Window Approach' to find the length of the longest substring without repeating characters within the input string.

Now what is sliding window approach? The sliding window approach is a technique used to solve problems involving arrays or strings, where the goal is to find a maximum or minimum value while maintaining a certain constraint. The constraint is often related to the size or the number of elements in a given subset of the array or string.

To proceed Start a for loop to iterate through each character of the input string. For each character, check if the character is not in the charMap object or if its value in the charMap object is less than the start variable. If either of these conditions is true, the current length of the substring (currLen) is incremented. If neither of these conditions is true, check if the current length of the substring is greater than the maximum length of the substring. If it is, update the maximum length of the substring.

Then current length of the substring is set to the difference between the 'current index' and the 'index of the character' in the 'charMap object'. Update start variable to be the value of the character in the charMap object plus 1. Add character and its index to the charMap object.

After the for loop completes, check one last time if the current length of the substring is greater than the maximum length of the substring. If it is, update the maximum length of the substring. Return the maximum length of the substring.

Call the function with the string and it should return the maximum length of substring without repeating characters. For webstylepress it's 8 for 'bstylepr'.

So this is how you can find length of longest substring without repeating characters using JavaScript and crack the javascript interview.

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It can be a good javascript interview question or frontend interview question. You may not be required to solve it on paper or whiteboard but the interviewer may ask you to give an idea on how to approach this algorithm. If you have an understanding of how to solve this problem or approach this algorithm, you will be able to answer it and get your next job as a frontend developer or full-stack developer.

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