public class Solution {
  public int strstr(String large, String small) {
    // write your solution here
    if (large == null || small == null) {
      return -1;
    }
    for (int i = 0; i < large.length() - small.length() + 1; i++) {
      int cur = i, j = 0;
      for (j = 0; j < small.length(); j++) {
        if (cur < large.length() && large.charAt(cur) != small.charAt(j)) {
          break;
        }
        cur++;
      }
      if (j == small.length()) {
        return i;
      }
    }
    return -1;
  }
}