public class Solution {
public String strStr(String haystack, String needle) {
// Start typing your Java solution below
// DO NOT write main() function
if(needle.length() == 0)
return haystack;
if(haystack.length() == 0)
return null;
int i = 0, j = 0;
while(i < haystack.length() && j< needle.length() ){
if(haystack.charAt(i) == needle.charAt(j)){
i++;
j++;
if(j==needle.length()){
return haystack.substring(i-j);
}
}
else{
i = i-j+1;
j=0;
}
}
return null;
}
}