Reverse words in a string 🙅‍♂️ In-place algorithm explained. Leetcode 186, 151, 557

Reverse Words in a String with space removal is an awesome problem to practice .. Every interview aspirant must practice it. Watch it multiple times to master these tricks and techniques that I am teaching here. This problem involves the famous two pointers' technique and the mirror reverse method.

All this solution have Time O(N) and Space O(1) complexities

0:00 Introduction
1:30 Reverse words in a sentence (LC - 557)
7:16 Intro to the second problem
8:21 Reverse sentence by words (LC - 186)
12:54 Reverse sentence by words skip spaces (LC - 151)
23:25 Final Take-Aways

Leetcode problem links :

#reversewords #leetcode #interviewdose

"never say never" Reverse Words in a String problem will master you in pointers manipulation "Step by Step" :)

My intention is not just to show you the solutions here but it's a **step by step** approach that someone should take while solving a problem in the real interview when he doesn't know a solution. Trust me it will be worth your session. feel free to share your feedback.

[chrisyeung]

Best explanation of this problem on YouTube! Salute to you sir this is excellent!

[mayankjain]

Excellent explanation, Keep up the good work!

[princepatoliya]

really good approach, explanation with multiple examples that's great for understanding. applaud🚀🚀

[alhaithamaljabri]

Thank you, Sir! Great Video! Well explained!

[prateekjhabak]

Very concise and clear solution..!! Kudos..!

[natureculturefoodlover]

I saw you wrote for loop in different way. For(;i <j; i++, j--). This is something new. Is this the different way to write for loop? Can you please explain?

[amandeepak]

Very nice concept and very well elaborated. Thankyou so much sir for clearing my concept. Would like to see more lectures like this., 👍

[tusharnain]

Many peoples mentioned to use stack in the last leetcode problem you explained, is it enough to know that?

[mehdinouira]

can you please explain this code to me, it is very complicated

[alisonlee]

Sir, I have tried to follow your tutorial but I am unable to get the expected output. Can you please provide some feedback? Here is my code:

class Solution {
//mirror image
void reverse(char[]str, int i, int j){
for(;i<j;i++, j--){
char temp=str[i];
str[i]=str[j];
str[j]=temp;
}
}

public String reverseWords(String s) {

char[]str=s.toCharArray();

int i=0;//backward pointer
int j=0;//forward pointer

while(j<=str.length){
if(j==str.length || str[j]== ' '){
reverse(str, i, j-1);
i=j+1;
}
j++;
}
return new String(str);
}
}