leetcode 28. Implement strStr()

Seawolf

1. Implement strStr().
   
2. 
   
3. Return the index of the first occurrence of needle in haystack, or -1 if needle is not part of haystack.
   
4. 
   
5. Example 1:
   
6. 
   
7. Input: haystack = "hello", needle = "ll"
   
8. Output: 2
   
9. Example 2:
   
10. 
    
11. Input: haystack = "aaaaa", needle = "bba"
    
12. Output: -1
    
13. Clarification:
    
14. 
    
15. What should we return when needle is an empty string? This is a great question to ask during an interview.
    
16. 
    
17. For the purpose of this problem, we will return 0 when needle is an empty string. This is consistent to C's strstr() and Java's indexOf().

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1. class Solution {
   
2.     public int strStr(String haystack, String needle) {
   
3.         
   
4.         int l1 = haystack.length();
   
5.         
   
6.         int l2 = needle.length();
   
7.         
   
8.         for(int i = 0; i< l1 - l2 + 1; i ++){
   
9.             
   
10.             // System.out.println(haystack.substring(i,i+l2));
    
11.             
    
12.             if(haystack.substring(i,i+l2).equals(needle)){
    
13.                
    
14.                 return i;
    
15.             }
    
16.         }
    
17.         
    
18.         return -1;
    
19.         
    
20.     }
    
21. }

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