diff --git a/Week_02/id_5/LeetCode_1_05.java b/Week_02/id_5/LeetCode_1_05.java
new file mode 100644
index 00000000..2db8ac60
--- /dev/null
+++ b/Week_02/id_5/LeetCode_1_05.java
@@ -0,0 +1,28 @@
+import java.util.HashMap;
+import java.util.Map;
+
+public class LeetCode_1_05 {
+
+    /**
+     * 两数之和
+     * - 做这个题的时候，已经做了三数之和了。
+     * - 那我就不再使用枚举的方法了
+     * -
+     * @param nums
+     * @param target
+     * @return
+     */
+    public int[] twoSum(int[] nums, int target) {
+        Map<Integer,Integer> book = new HashMap<>();
+        for (int i = 0;i<nums.length;i++){
+            int resultNum = target - nums[i];
+            if (book.containsKey(resultNum)){
+                return new int[]{book.get(resultNum),i};
+            }
+            book.put(nums[i],i);
+        }
+       return null;
+    }
+
+
+}
diff --git a/Week_02/id_5/LeetCode_3_05.java b/Week_02/id_5/LeetCode_3_05.java
new file mode 100644
index 00000000..904fe6e0
--- /dev/null
+++ b/Week_02/id_5/LeetCode_3_05.java
@@ -0,0 +1,30 @@
+import java.util.HashSet;
+
+public class LeetCode_3_05 {
+
+    /**
+     * 计算 字符串中不含有重复字符的最大子串的长度
+     * - 要点 滑动窗口 HashSet
+     *
+     * @param s
+     * @return
+     */
+    public int lengthOfLongestSubstring(String s) {
+        int length = s.length();
+        HashSet<Character> window = new HashSet<>();
+        int i = 0, j = 0, maxLength = 0;
+
+        while (i < length && j < length) {
+            if (!window.contains(s.charAt(j))) {
+                window.add(s.charAt(j));
+                j++;
+                maxLength = Math.max(maxLength, j - i);
+            }else{
+                window.remove(s.charAt(i));
+                i++;
+            }
+        }
+        return maxLength;
+    }
+
+}