Longest substring without repeating characters

          You are tasked with developing a function that finds 
          the length of the longest substring without repeating 
          characters in a given string s.
          Consider different scenarios involving various 
          characters in the input string.
          Scenario: String with No Repeating Characters 
          Input: "abcdef"
          Expected Output: 6
          Explanation: In this scenario, the input string contains
          no repeating characters, so the entire string itself is the longest substring without repeating characters.
          Scenario: String with Repeating Characters
          Input: "abccba"
          Expected Output: 3
          Explanation: In this case, the longest substring without repeating characters is "abc" with a length of 3. The characters 'c' and 'b' are repeated, so the substring ends at the first occurrence of the repeated character
         
         
          Exercise-1
          Input:
          pqrsstu
          Output: 4
          
          
          Exercise-2
          Input:
          abbedfgi
          Output: 6
          

        

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Java code :--

 
         

import java.util.HashMap; 
import java.util.Scanner; 
 
public class MINtech { 
 
    public static int lengthOfLongestSubstring(String s) { 
        // Initialize a HashMap to store the last index of each character 
        HashMap lastIdxMap = new HashMap<>(); 
        // Initialize variables to keep track of the start of the current substring and the length of the longest substring 
        int start = 0; 
        int maxLength = 0; 
 
        // Iterate through the characters of the string 
        for (int end = 0; end < s.length(); end++) { 
            // If the current character is already in the substring, update the start index 
            if (lastIdxMap.containsKey(s.charAt(end)) && lastIdxMap.get(s.charAt(end)) >= start) { 
                start = lastIdxMap.get(s.charAt(end)) + 1; 
            } 
 
            // Update the last index of the current character 
            lastIdxMap.put(s.charAt(end), end); 
 
            // Update the length of the longest substring if needed 
            maxLength = Math.max(maxLength, end - start + 1); 
        } 
 
        return maxLength; 
    } 
 
    public static void main(String[] args) { 
        // Get user input for the string 
        Scanner scanner = new Scanner(System.in); 
        System.out.print("Enter any string :- "); 
        String inputString = scanner.nextLine(); 
 
        // Calculate and print the length of the longest substring without repeating characters 
        int result = lengthOfLongestSubstring(inputString); 
        System.out.println("Length of the longest substring without repeating characters :--  " + result); 
    } 
} 

         

Output

      Enter any string :- pqrsstu
      Length of the longest substring without repeating characters :--  4


      Enter any string :- abbedfgi
      Length of the longest substring without repeating characters :--  6
  
        

Python code :---

  
       

def length_of_longest_substring(s): 
    # Initialize a dictionary to store the last index of each character 
    last_index = {} 
    # Initialize variables to keep track of the start of the current substring and the length of the longest substring 
    start = 0 
    max_length = 0 
 
    # Iterate through the characters of the string 
    for end in range(len(s)): 
        # If the current character is already in the substring, update the start index 
        if s[end] in last_index and last_index[s[end]] >= start: 
            start = last_index[s[end]] + 1 
 
        # Update the last index of the current character 
        last_index[s[end]] = end 
 
        # Update the length of the longest substring if needed 
        max_length = max(max_length, end - start + 1) 
 
    return max_length 
 
# Get user input for the string 
input_string = input("Enter any string :-- ") 
 
# Calculate and print the length of the longest substring without repeating characters 
result = length_of_longest_substring(input_string) 
print("Length of the longest substring without repeating characters :--  ", result) 

       
 

Output

      Enter any string :- pqrsstu
      Length of the longest substring without repeating characters :--  4


      Enter any string :- abbedfgi
      Length of the longest substring without repeating characters :--  6