Good afternoon! Here's our prompt for today.

Given a string of characters, can you find the longest substring of the string that has no repeating characters?

An example is shown below:

1lengthOfLongestSubstring("abracadabar");
2// 4 because it is 'brac'

Constraints

• Length of the string <= 100000
• The string will only contain lowercase letters
• Expected time complexity : O(n)
• Expected space complexity : O(1)

In this challenge, we'll discuss a simple but efficient method for finding the longest substring with no repeating characters.

Try to solve this here or in Interactive Mode.

How do I practice this challenge?

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var assert = require('assert');

​

var lengthOfLongestSubstring = function (s) {

  // fill this in

  return maximumLen;

};

​

try {

  assert.equal(lengthOfLongestSubstring('algodaily'), 7);

​

  console.log(

    'PASSED: ' +

      "`lengthOfLongestSubstring('algodaily')` should be equal to `7`"

  );

} catch (err) {

  console.log(err);

}

​

try {

  assert.equal(lengthOfLongestSubstring('thisisatest'), 5);

​

  console.log(

    'PASSED: ' +

      "`lengthOfLongestSubstring('thisisatest')` should be equal to `5`"

  );

} catch (err) {

  console.log(err);

}

​

Here's our guided, illustrated walk-through.

How do I use this guide?