Implement strStr()

Implement strStr().

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

Update (2014-11-02):
The signature of the function had been updated to return the index instead of the pointer. If you still see your function signature returns a

char *

or

String

, please click the reload button to reset your code definition.

public class Solution {
public int strStr(String haystack, String needle)
{
if(needle.length()==0)
return 0;

for (int i=0;i<haystack.length();i++)
{
if (haystack.length() - i +1 < needle.length())
return -1;

int j = 0;
int k = i;

while(j<needle.length()&&k<haystack.length()&&needle.charAt(j)==haystack.charAt(k))
{
j++;
k++;
if(j==needle.length())
return i;
}

}

return -1;
}
}