Implement strStr().
Return the index of the first occurrence of needle in haystack, or -1 if needle is not part of haystack.
Example 1:
Input: haystack = “hello”, needle = “ll”
Output: 2
Example 2:
Input: haystack = “aaaaa”, needle = “bba”
Output: -1
public class Solution {
public int strStr(String haystack, String needle) {
int l1 = haystack.length(), l2 = needle.length();
if (l1 < l2) {
return -1;
} else if (l2 == 0) {
return 0;
}
int threshold = l1 - l2;
for (int i = 0; i <= threshold; ++i) {
if (haystack.substring(i,i+l2).equals(needle)) {
return i;
}
}
return -1;
}
}