Reverse words in a string

This video explains how to reverse words in a string. This is one of the most frequently asked interview and coding round question for software companies. My microphone got damaged and hence the sound quality is way below par but i am trying to get it fixed as soon as i can. If you find any difficulty or have any query then do COMMENT below. PLEASE help our channel by SUBSCRIBING and LIKE our video if you found it helpful...CYA :)

[anushraghav]

@Tech dose How to solve this problem using space O(1) and recursion?

[MKSundaram]

If suppose I want to swap only certain words in the string, how can I do it?
example: John knows Python and Sundar knows Java
I want to swap Java with Python and Python with Java.
There are solutions on net, but NO one explains like you do.
Thanks :-)

[sushant]

I CAME HERE FOR CODE. I KNOW THE APPROACH. BUT DOING SOME MISTAKE IN CODING PART, BUT THIS NOT COVERED

[AnjaliKumari-zmzo]

I really love all the videos of your channel. Could you please provide the code link of your explanation? It will be really helpful

[varunsadhu]

Hi Budy, i have started to like your videos lot. And really appreciate ur help. Just one suggestion try to cover the solutions in constant space as well. It will help everyone :) thanks

[chetanraghavv]

I got approach instantly but did not know why was getting error in implementing.
Took a lot of time in getting the mistake! Leaving my working C++ code here so others can refer:

class Solution {
public:
string reverseWords(string s) {
string res;
int n = s.length();
//s = " how are you "
//Firstly remove all the excessive spaces
if(s[0] != ' ')
res.push_back(s[0]);
for(int i=1; i<n; i++)
{
if(s[i] != ' ')
res.push_back(s[i]);

else if(s[i] == ' ' && s[i-1] != ' ') //insert space only after word ends so when s[i] is ' ' but s[i-1] is not, this means the word has ended
res.push_back(' ');
}
if(res.back() == ' ') //we do not want space after the last word
res.pop_back();

int r = res.length();
int countSpaces = 0;
for(int i=0; i<r; i++)
{
if(res[i] == ' ')
countSpaces++;
}
if(countSpaces == 0) //if only one word is present in string, return as it is
return res;
// res = "how are you"
//Now we need to reverse the whole string and then reverse each word
for(int i=0; i<r/2; i++)
swap(res[i], res[r-1-i]); //res = "uoy era woh"

int i, j=0;
for(i=0; i<r; i++) //reversing each word
{
if(res[i] == ' ') //when ' ' is reached, start of any word is given by j and end is given by i-1. j is updated everytime a previous word is reversed. for the last word, j stands at start of last word and i becomes equal to res.size(). Handle last word separately
{
for(int start=j, end=i-1; start < end; start++, end--)
swap(res[start], res[end]);
j = i+1;
}
}
//after for loop ends, j will be at starting of last word and i will be at 1 vaue ahead of end of last word
for(int start=j, end=i-1; start < end; start++, end--)
swap(res[start], res[end]);
return res;
}
};

[dewanganskitchen]

Hi sir can you please tell me how to reverse a word like
I like java
a vaje kili

[rajatarora]

We can split string on the basis of space and traverse it from end, this will also do the task

[DhruvilPatel]

Dude, you are great! The way you explain is by far to the point. Thks a lot!

[sakthim]

Even i guess the logic when I saw the problem statement. Is this the only way to do this? There is no other way?

[babuk]

int main ()
{
int i, j, c=0;
char s [50], temp [50];
gets (s);
for (i=0;s [i]!='\0';i++)
c=c+1;
for (i=c-1, j=0;i>=0;i--, j++)
{
temp [j]=s[i];
}
printf ("%s\n", temp);
return 0;
}
Sir i did upto this sir. I reverse entire string and then how to reverse each and every word . As you said in the class.

[prasad.patil]

Superb 👍
Can you explain your thought process while approaching such a tricky problem?

[srividhyaparthasarathy]

@Tech dose where can i find the code for this in c++

[amitpaunikar]

Awesome explaination sir....pls add more videos on time and space complexity

[bharatnagasunil]

input :she is good
iam getting output as good si ehs the next two words are not reversing help me

[sainathreddy]

code :)

#include<bits/stdc++.h>
using namespace std;

int main()
{
// reversing the words
string st;
cout<<"enter the string";
getline(cin, st);
int i =0 ;
cout<<"\n";
int n = st.length();
// reversing the entire string
for(int i = 0; i <n/2;i++)
{
swap(st[i], st[n-i-1]);
}
int start =0;
char temp;
int j =0;

// revversign the string with gap as end
for(i=0;i<n;i++)
{
if(st[i]==' ' || st[i]=='\0')
{
for(int begin=j, end=i-1 ; begin<(i+j)/2 ; begin++, end--)
{
swap(st[begin], st[end]);
}
j=i+1;
}
}
// printing the string
for(int i = 0 ; i <n;i++)
{
if(st[i] == ' ')
{
cout<<"\n";
}
else
{
cout<<st[i];
}

}
return 0;
}

[shariquekalam]

@techdose from where can i learn the time complexity, i mean i need tutorials to calculate the time compley of the codes

[jasmeenkaur]

can u provide the code of this logic??

[atharvaverma]

Code -
class Solution {
public:
string reverseWords(string s) {
s.push_back(' ');
string ans ="";
stack<string> st;
string temp="";
for(int i=0;i<s.size();i++){
if(s[i]!=' '){
temp.push_back(s[i]);
}
else if(temp.size()!=0){
st.push(temp);
temp="";
}
}
while(!st.empty()){
ans+=st.top();
ans+=' ';
st.pop();
}
ans.pop_back();
return ans;
}
};

[LetszGoo]

These 106 people who dislike this video .those who are in 4th year and their placements are about to come .