feat: add 028

Author: Blankj

README.md

@@ -17,6 +17,7 @@
 |21|[Merge Two Sorted Lists][021]|Linked List|
 |26|[Remove Duplicates from Sorted Array][026]|Array, Two Pointers|
 |27|[Remove Element][027]|Array, Two Pointers|
+|28|[Remove Element][028]|Array, Two Pointers|
 
 
 ## Medium
@@ -48,3 +49,4 @@
 [021]: https://github.com/Blankj/awesome-java-leetcode/blob/master/note/021/README.md
 [026]: https://github.com/Blankj/awesome-java-leetcode/blob/master/note/026/README.md
 [027]: https://github.com/Blankj/awesome-java-leetcode/blob/master/note/027/README.md
+[028]: https://github.com/Blankj/awesome-java-leetcode/blob/master/note/028/README.md

note/028/README.md

@@ -0,0 +1,39 @@
+# [Implement strStr()][title]
+
+## Description
+
+Implement strStr().
+
+Returns the index of the first occurrence of needle in haystack, or -1 if needle is not part of haystack.
+
+**Tags:** Two Pointers, String
+
+
+## 思路
+
+题意是从主串中找到子串的索引，如果找不到则返回-1，我们只需要遍历主串长度减字串长度即可，利用substring比较即可。
+
+``` java
+public class Solution {
+    public int strStr(String haystack, String needle) {
+        int l1 = haystack.length(), l2 = needle.length(), l3 = l1 - l2;
+        int l3 = l1 - l2;
+        for (int i = 0; i <= l3; ++i) {
+            if (haystack.substring(i, i + l2).equals(needle)) {
+                return i;
+            }
+        }
+        return -1;
+    }
+}
+```
+
+
+## 结语
+
+如果你同我一样热爱数据结构、算法、LeetCode，可以关注我GitHub上的LeetCode题解：[awesome-java-leetcode][ajl]
+
+
+
+[title]: https://leetcode.com/problems/implement-strstr
+[ajl]: https://github.com/Blankj/awesome-java-leetcode

project/LeetCode/leetcode/src/main/java/com/blankj/easy/_028/Solution.java

@@ -0,0 +1,28 @@
+package com.blankj.easy._028;
+
+/**
+ * <pre>
+ *     author: Blankj
+ *     blog  : http://blankj.com
+ *     time  : 2017/04/21
+ *     desc  :
+ * </pre>
+ */
+
+public class Solution {
+    public int strStr(String haystack, String needle) {
+        int l1 = haystack.length(), l2 = needle.length(), l3 = l1 - l2;
+        for (int i = 0; i <= l3; ++i) {
+            if (haystack.substring(i, i + l2).equals(needle)) {
+                return i;
+            }
+        }
+        return -1;
+    }
+
+    public static void main(String[] args) {
+        Solution solution = new Solution();
+        System.out.println(solution.strStr("12345", "23"));
+        System.out.println(solution.strStr("12345", ""));
+    }
+}