Leetcode 3 | Longest Substring Without Repeating Characters | solution

 Longest Substring Without Repeating Characters 

Given a string s, find the length of the longest substring without repeating characters.

 

Example 1:

Input: s = "abcabcbb"
Output: 3
Explanation: The answer is "abc", with the length of 3.

Example 2:

Input: s = "bbbbb"
Output: 1
Explanation: The answer is "b", with the length of 1.

Example 3:

Input: s = "pwwkew"
Output: 3
Explanation: The answer is "wke", with the length of 3.
Notice that the answer must be a substring, "pwke" is a subsequence and not a substring.

 

Constraints:

• 0 <= s.length <= 5 * 104
• s consists of English letters, digits, symbols and spaces.

solution: 

This solution is done through unordered_map in c++. These are like hashmap in java .

following is the solution : 

class Solution {

public:

    int lengthOfLongestSubstring(string s) {

        unordered_map<char, int>um;

        int l = s.length();

        int j = 0;

        int length = 0;

        for(int i =0; i < l ; i++)

        {

            if(!um.count(s[i]))

            {

                um[s[i]] = 1;

            }

            else

            {

               um[s[i]] ++;

            }

            while(um[s[i]] > 1 )

            {  

                                

               if(s[j] == s[i])

               {

                    um[s[i]] -- ;

               }

                else

                um[s[j]]--;

                

                j++;

             }

             

              

            if(i - j +1 > length)

            {

              length = i -j+1;

            }

        }

        return length;

             

        }

        

    

};