Java Program To Find Longest Substring Without Repeated Character | Ashok IT

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[@lakshmidevilakshmidevi3984]

Excellent explanation.Esay approach.Thank you.

[@ashokit]

You are welcome!

[@ayushsingh3967]

Your code would get fail if input string is like s ="abcbdaac" because you'r replacing the i value with map.get(ch) but in this case i should be replaced as map.get(ch) -1 as it has to include character "c" when second b is get encountered.

[@shikharrawat4388]

Even replacing it by map.get(ch) -1 doest yeild the proper output

[@thiestmayank]

Ther's no problem with the code WRT to your input i.e "abcbdaac" I'm getting the correct output
longest substring is : [c, b, d, a]
longest substring length is : 4
NOTE: based on your input ---> i = map.get(ch); duplicate 'b' found at 3rd index but from the String first time 'b' occurred at 1st index
and due to i++ loop control will be increased to i=2 and at second index we have 'c'
finally getting the output as expected.

[@manishjoshi539]

public static int findL(String s) {
int l = s.length();
int a_pointer = 0;
int b_pointer = 0;
int max = 0;
HashSet hashSet = new HashSet();
while (b_pointer < l) {
if (!hashSet.contains(s.charAt(b_pointer))) {
hashSet.add(s.charAt(b_pointer));
b_pointer++;
max = Math.max(hashSet.size(), max);
} else {
hashSet.remove(s.charAt(a_pointer)); //
a_pointer++; // to iterate to next pointer since the current pointer is removed in the previous step
}
}
return max;
}

[@kartikeyachoudhary5742]

it's only good when you want an int type return value but this program won't be able to print the subarray string.

[@vaibhavnirmal1]

Thank you sir this was amazing series on string!

[@raghvendrasinghkushwah8293]

Really helpful :), thanks for this video.

[@ashokit]

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[@PBtelugu]

Super Logic sir

[@kogulselvanathan4218]

Hi, sir while explaining use debugging mode so that it will easy to understand more clearly. Anyways, nice tutorial.

[@maheshbabu9909]

wow ur awesome sir

[@dhanushakian5910]

import java.util.LinkedHashMap;
import java.util.Map;
class Solution {
public static void lengthOfLongestSubstring(String s) {
String longestSubstring = null;
int lengthOfLongestSubstring = 0;
Map map = new LinkedHashMap();
char[] arr = s.toCharArray();
int start = 0;
for (int i = 0; i < arr.length; i++) {
char ch = arr[i];
if (map.containsKey(ch)) {
start = Math.max(start, map.get(ch) + 1);
}
map.put(ch, i);
if (i - start + 1 > lengthOfLongestSubstring) {
lengthOfLongestSubstring = i - start + 1;
longestSubstring = s.substring(start, i + 1);
}
}
System.out.println(lengthOfLongestSubstring);
System.out.println(longestSubstring);
}
public static void main(String[] args) {
lengthOfLongestSubstring("rsdhghkhjdrsbng");
}
}
proper working code for all string inputs

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[@rahulsingh-jg9wt]

Thanks

[@my_love_sanatan]

Map will clear whole values inside Map??

[@srikanthchincholi481]

Yes, it should otherwise repeated chars will be strored

[@RISHIKA_REDDY555]

the code will fail for ip:abac it gives 2 as op but the correct ans is 3 beacuse bac is longest sub string with no repeated character ...in your code we are not taking previous character!!!!!!!!!!!!

[@ashokit]

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[@gauravpalkar3885]

This code is failing.

[@AdityaKumar-ym3fy]

Kinda too time taking approach, but working
String s1 = "abac";
String longestStr = "";
String currentStr = "";

Set charSet = new LinkedHashSet();

for(int i = 0; i < s1.length(); i++) {
for(int j = i; j < s1.length(); j++) {
char ch = s1.charAt(j);
if( !charSet.contains(ch) ) {
charSet.add(ch);
}
else if( charSet.contains(ch) )
{
currentStr = charSet.toString();
if(currentStr.length() > longestStr.length()) {
longestStr = currentStr;
}
charSet.clear();
currentStr = "";
break;
}


}
}

System.out.println(longestStr);

[@NishantKumar0786]

nice logic

[@rjoker60]

else block is not clear , why are you getting index value and setting it to i

[@srikanthchincholi481]

If char repeated we should clear it otherwise we may get chars repeated and here taking index to start freshly to check for substring

[@gauravpalkar3885]

Even I got the same question ? It's not working fine.

[@Anil--hs1fb]

@@gauravpalkar3885true

[@tricksforsolving2804]

i am not able to understand what else part doing

[@ashokit]

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[@maheshmagarde2143]

Sir I written same program it is giving wrong answer if I pass string "aabb" it rutering 1 insted of 2.....?

[@prajwalgvaishnav4991]

The answer is 1 only since it should be "without repeating the characters " . Here "aa" substring is invalid. The correct answer is "a"

[@srihari4827]

answer is 2 which is ab

[@gauravpalkar3885]

Yes it is giving wrong result. I changed the program and its now working fine.

[@AbhishekSingh-h6s]

Hi Sir,
This code is not working:
public static void main(String [] args) {
lengthoflongestsubstring("java");

}
public static void lengthoflongestsubstring(String s) {
String longestsubstring = null;
int longestsubstringlength = 0;
Map map = new LinkedHashMap();
char [] arr = s.toCharArray();
for (int i = 0; i < arr.length; i++) {
char ch = arr[i];
if (!map.containsKey(ch)) {
map.put(ch, i);
}
else {
i= map.get(ch);
map.clear();
}
if (map.size()>longestsubstringlength) {
longestsubstringlength = map.size();
longestsubstring = map.keySet().toString();
}
}}

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[@RichaBehera129]

why we are removing the map

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[@akhouritushar]

This code wont work for string ABCDEFGABEF

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