Find the Index of the First Occurrence in a String | Google, Microsoft | Leetcode 28

This is the 14th Video of our Strings Playlist.
In this video we will try to solve another very good and popular problem "Find the Index of the First Occurrence in a String - Leetcode 28"

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Problem Name : Find the Index of the First Occurrence in a String
Company Tags : Google, Amazon, Microsoft, Facebook, Qualcomm

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[JJ-tpdd]

Thanks, bhai. Below is the JAVA implementation:

class Solution {
public int strStr(String s1, String s2) {
int m = s1.length();
int n = s2.length();

for(int i=0; i<m-n+1; i++) {
for(int j=0; j<n; j++) {
if(s1.charAt(i+j) != s2.charAt(j)) {
break;
}
if(j == n-1) {
return i;
}
}
}
return -1;
}
}

[aryansinha]

Your voice is good, the audio was clear and bold and you explained so well. Thank you.

[taneyasoni]

congratulations on 8k subs. Please try to cover questions from popular SDE sheets that engineering students are following(these days) meanwhile I wish you all the best for your own SDE sheet.

I am following two things 1- POTD leetcode 2- a popular SDE sheet I found on the web. For both things, I first search for your solutions.

[HealthyOm]

Ur efforts is really really gold producers love u bhaiya ❤️❤️❤️❤️

[prathamtetgure]

Aapke jaisa banna hai, aapki coding journey share karo pls

[itspravas]

After the first for loop you can add an if condition which will check if first letter of needle is same as current letter of haystack, so that we won't go inside the second for loop, for each character of haystack.

[siddharthsinghbhadoria]

Well explained!!! Bro when are you uploading KMP and Rabin karp alg videos?

[arunsharma]

Thanks for the explanation
Please provide videos of kmp and rabin karp

[harsh.jain]

This is O(n) solution in java : 0ms runtime

class Solution {
public int strStr(String haystack, String needle) {
int n = haystack.length();
int strLen = needle.length();

for(int i=0; i<=n-strLen; i++){
if( haystack.substring(i, i+strLen).equals(needle) ){
return i;
}
}
return -1;
}
}

[rohitsingh]

(Minimum Fuel Cost to Report to the Capital )

Hii sir please make video of above question

[best]

How's this one?

class Solution {
public:
int strStr(string haystack, string needle) {
int m = haystack.size();
int n = needle.size();
for(int i=0 ; i<m ; i++)
{
if(haystack.substr(i, n)==needle) return i;
}
return -1;

}
};

[csepratikshaargulewar]

Could anyone share brute force approach?

[arunsharma]

What is the complexity if we use while loop..
int strStr(string haystack, string needle) {
int m = haystack.length();
int n = needle.length();
int count = 0;
int i= 0, j=0;
while(i<m && j<n)
{
if(haystack[i+j] == needle[j])
{
count++;
if(count == n )
{
return i;
}
j++;
}
else
{
i++;
count = 0;
j = 0;
}
}
return -1;
}

[naveenrajput]

for(int
if(s1.substring(i, i+s2.length()).equals(s2))
return i;


return -1;

[yuvrajbhardawaj]

class Solution {
public int strStr(String haystack, String needle) {

return -1;
for(int
int j=i;
while(j-i<needle.length() && j<haystack.length() &&
j++;
if(j-i==needle.length())
return i;
}
return -1;
}
}

[ektuhaso]

Sir please make a video on rabin karp algorithm please sir 😭

[vishalplayzz]

this is also fine right ?
code :
class Solution {
public:
int strStr(string haystack, string needle) {
int n=needle.length();
int i=0;
int j=0;
while(i<haystack.length())
{
if(j==n)return i;
else
else{
i++;
j=0;
}
}
return -1;
}
};

[samir]

vai kmp and rabin karp ki video bnado eagarly waiting for it

[ezcoding]

12:14 agar dekha jaye to udhar se hi i return krega ....lekin internally kya loop chalega return ke bad v ?

[yashgarg]

Bhai can you tell me complexity of this code pleaseee
class Solution {

public int strStr(String haystack, String needle) {
String match = needle;
String ans = "";
int j=0;
int i=0;
while(j < haystack.length()){
ans += haystack.charAt(j);
if(j-i+1 < needle.length()) j++;
else if(match.equals(ans)){
return i;
}
else{
ans = ans.substring(1);
i++;
j++;
}
}
return -1;
}
}