How should I practice Longest Substring Without Repeating Characters?

Start by reading the full statement, solve the visible examples, then compare the pattern against related IBM phone screen problems in FastPrep.

Is Longest Substring Without Repeating Characters associated with IBM?

FastPrep tags this as a IBM phone screen coding practice problem when the problem catalog has that company and stage context.

Longest Substring Without Repeating Characters

IBM● MediumFULLTIMEPHONE SCREEN

Problem statement

Given a string s, return the length of the longest substring of s in which no character appears more than once.

A substring is a run of consecutive characters. Characters are compared exactly: uppercase and lowercase letters are different characters, and spaces, digits, and symbols are characters too.

If s is empty, return 0.

Function

lengthOfLongestSubstring(s: String) → int

Examples

Example 1

s = "hello world"return = 6

The longest substring with no repeated character is " world": a space followed by world, 6 characters in all.

Any longer substring repeats a character. For example, "o world" has 7 characters and repeats o.

Example 2

s = "abba"return = 2

"ab" and "ba" both have length 2. Every substring of length 3 repeats b, so the answer is 2.

When the last a arrives, the window is already "b" after the repeated b, so the first a is no longer inside it.

Example 3

s = "Bob met Tom"return = 7

"Bob met" has 7 different characters: B and b are different, and the space counts once. The next character is a second space, so no longer substring works there, and no other substring is longer than 7.

Constraints

0 <= s.length <= 5 * 10^4
s contains only printable ASCII characters: English letters, digits, spaces, and symbols.