Implement strStr()

Implement strStr().

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

Tips:

没啥Tips，复杂度应该是O(nk)。

Code:

public class Solution {
    public int strStr(String haystack, String needle) {
      for (int i = 0; ; i++) {
        for (int j = 0; ; j++) {
          if (j == needle.length()) return i;
          if (i + j == haystack.length()) return -1;
          if (needle.charAt(j) != haystack.charAt(i + j)) break;
        }
      }
    }
}