3. Longest Substring without repeating characters "Leetcode" Java, algorithm, Substring implementation, SUBSTRING, HASHMAP

3. Longest Substring without repeating characters

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

Examples:

Given "abcabcbb" , the answer "abc" is, which the length is 3.

Given "bbbbb" , the answer "b" is, with the length of 1.

Given "pwwkew" , the answer "wke" is, with the length of 3. Note that the answer must was a substring, is "pwke" a subsequence and not a substring.

Problem:

Given a string, the length of the longest substring is found without repeating characters.
Instance:
"ABCABCBB", the answer is "ABC", its length is 3.
"BBBBB", the answer is "B", the length is 1.
"Pwwkew", the answer is "Wke", to 3 of the length. Note that the answer must be a string, and "Pwke" is a substring.

Implementation method:

1. Get the string length
2. Record the current value is left mark
3. Determine if the current letter has occurred, and if so, update the current position to a new left tag
4. Update res length If current value is larger than res

Method: Use HashMap to skip loops and save time and space when you encounter duplicates

1  Public classSolution {2      Public intlengthoflongestsubstring (String s) {3map<character,integer> map =NewHashmap<>();4         intRes =0,len=s.length ();5          for(inti=0,j=0;j<len;j++){6             if(Map.containskey (S.charat (j))) {7I=Math.max (Map.get (S.charat (j)), I);8             }9Map.put (S.charat (j), j+1);TenRes =math.max (j-i+1, res); One         } A         returnRes; -     } -}

3. Longest Substring without repeating characters "Leetcode" Java, algorithm, Substring implementation, SUBSTRING, HASHMAP