diff --git a/com/zerroi/leetcode/ThreeThree/First.java b/com/zerroi/leetcode/ThreeThree/First.java
index 3f50693..0e405cc 100644
--- a/com/zerroi/leetcode/ThreeThree/First.java
+++ b/com/zerroi/leetcode/ThreeThree/First.java
@@ -4,7 +4,7 @@ public class First {
 
 }
 
-class Solution {
+class SolutionFirst {
     public String intToRoman(int num) {
         String[] a1 = new String[] { "I", "IV", "V", "IX", "X", "XL", "L", "XC", "C", "CD", "D", "CM", "M" };
         int[] a2 = new int[]{1, 4, 5, 9, 10, 40, 50, 90, 100, 400, 500, 900, 1000};
diff --git a/com/zerroi/leetcode/ThreeThree/Second.java b/com/zerroi/leetcode/ThreeThree/Second.java
new file mode 100644
index 0000000..578b20c
--- /dev/null
+++ b/com/zerroi/leetcode/ThreeThree/Second.java
@@ -0,0 +1,16 @@
+package com.zerroi.leetcode.ThreeThree;
+
+import java.util.ArrayList;
+import java.util.List;
+
+public class Second {
+}
+
+class SolutionSecond {
+    public List<String> generateParenthesis(int n) {
+        List<String> res = new ArrayList<>();
+
+
+        return res;
+    }
+}
diff --git a/com/zerroi/leetcode/sort/BubbleSort.java b/com/zerroi/leetcode/sort/BubbleSort.java
new file mode 100644
index 0000000..08a930b
--- /dev/null
+++ b/com/zerroi/leetcode/sort/BubbleSort.java
@@ -0,0 +1,28 @@
+package com.zerroi.leetcode.sort;
+
+public class BubbleSort {
+    public static void main(String[] args) {
+        Bubble bubble = new Bubble();
+        int[] res = bubble.bubble(new int[]{2, 1, 9, 3, 10});
+        for (int item : res) {
+            System.out.println("item = " + item);
+        }
+
+    }
+}
+
+class Bubble {
+    public int[] bubble(int[] nums) {
+        for (int i = 0; i < nums.length - 1; i++) {
+            for (int j = 0; j < nums.length - i - 1; j++) {
+                int temp;
+                if (nums[j] > nums[j + 1]) {
+                    temp = nums[j];
+                    nums[j] = nums[j + 1];
+                    nums[j + 1] = temp;
+                }
+            }
+        }
+        return nums;
+    }
+}
diff --git a/com/zerroi/leetcode/sort/InsertionSort.java b/com/zerroi/leetcode/sort/InsertionSort.java
new file mode 100644
index 0000000..1811f77
--- /dev/null
+++ b/com/zerroi/leetcode/sort/InsertionSort.java
@@ -0,0 +1,30 @@
+package com.zerroi.leetcode.sort;
+
+public class InsertionSort {
+    public static void main(String[] args) {
+        Insertion insertion = new Insertion();
+        int[] ints = insertion.insertionSort(new int[]{2, 1, 9, 3, 10});
+        for (int item : ints) {
+            System.out.println("item = " + item);
+        }
+
+    }
+}
+
+class Insertion {
+    public int[] insertionSort(int[] nums) {
+        for (int i = 1; i < nums.length; i++) {
+             int temp = nums[i];
+             int j = i;
+             while (j > 0 && temp < nums[j - 1]) {
+                 nums[j] = nums[j - 1];
+                 j--;
+             }
+             if (j != i) {
+                 nums[j] = temp;
+             }
+        }
+
+        return nums;
+    }
+}
diff --git a/com/zerroi/leetcode/sort/SelectionSort.java b/com/zerroi/leetcode/sort/SelectionSort.java
new file mode 100644
index 0000000..0af71e5
--- /dev/null
+++ b/com/zerroi/leetcode/sort/SelectionSort.java
@@ -0,0 +1,35 @@
+package com.zerroi.leetcode.sort;
+
+/**
+ * 选择排序是一种简单直观的排序算法，无论什么数据进去都是 O(n²) 的时间复杂度。所以用到它的时候，数据规模越小越好。
+ * 唯一的好处可能就是不占用额外的内存空间了吧。
+ * 1. 算法步骤
+ * 首先在未排序序列中找到最小（大）元素，存放到排序序列的起始位置。
+ * 再从剩余未排序元素中继续寻找最小（大）元素，然后放到已排序序列的末尾。
+ * 重复第二步，直到所有元素均排序完毕。
+ */
+public class SelectionSort {
+    public static void main(String[] args) {
+        Selection selection = new Selection();
+        int[] res = selection.selection(new int[]{2, 1, 9, 3, 10});
+        for (int re : res) {
+            System.out.println(re);
+        }
+    }
+}
+
+class Selection {
+    public int[] selection(int[] nums) {
+        for (int i = 0; i < nums.length; i++) {
+            for (int j = i + 1; j < nums.length; j++) {
+                int temp = 0;
+                if (nums[i] > nums[j]) {
+                    temp = nums[i];
+                    nums[i] = nums[j];
+                    nums[j] = temp;
+                }
+            }
+        }
+        return nums;
+    }
+}