Implement strStr() or indexOf() Java Solution - The Coding Shala

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Implement strStr() or indexOf() Java Solution

Problem:



Return the index of the first occurrence of needle in the haystack, or -1 if the needle is not part of haystack.



Example 1:


Input: haystack = "hello", needle = "ll"
Output: 2

Example 2:

Input: haystack = "aaaaa", needle = "bba"
Output: -1

Implement strStr() or indexOf() Java Solution

Approach:
If the needle char does not match with haystack return -1 else continue checking.

Java 

class Solution {
    public int strStr(String haystack, String needle) {
        int len1 = haystack.length();
        int len2 = needle.length();
        if(len2 == 0) return 0;
        int index = -1;
        if(len2>len1) return -1;
        for(int i=0; i<len1; i++){
            int flag=0;
            if(haystack.charAt(i) == needle.charAt(0)){
                int tmp = i;
                int cnt = 0;
                while(tmp < len1 && cnt<len2){
                    if(haystack.charAt(tmp)!=needle.charAt(cnt)){
                        flag=1;
                        break;
                    }  
                    cnt++;
                    tmp++;
                }
                if(flag==0 && cnt==len2) { index = i; break;} 
            }
        }
        return index;
    }
}



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