diff --git a/3.排序算法/src/sort/exchange/BubbleSort.java b/3.排序算法/src/sort/exchange/BubbleSort.java
index 687d6e4..03ceedf 100644
--- a/3.排序算法/src/sort/exchange/BubbleSort.java
+++ b/3.排序算法/src/sort/exchange/BubbleSort.java
@@ -15,6 +15,7 @@ public class BubbleSort {
         int[] arr = {4, 12, 2, 8, 453, 1, 59, 33};
         for (int i = 0, length = arr.length; i < arr.length - 1; i++) {
             for (int j = 0, tempLength = length - 1 - i; j < tempLength; j++) {
+                //如果当前数大于下一个数那么和下一个数交换位置
                 if (arr[j] > arr[j + 1]) {
                     int temp = arr[j];
                     arr[j] = arr[j + 1];
diff --git a/3.排序算法/src/sort/exchange/CountSort.java b/3.排序算法/src/sort/exchange/CountSort.java
new file mode 100644
index 0000000..fcc44d9
--- /dev/null
+++ b/3.排序算法/src/sort/exchange/CountSort.java
@@ -0,0 +1,47 @@
+package sort.exchange;
+
+import java.util.Arrays;
+
+/**
+ * 类功能简述：计数排序
+ * 类功能详述：
+ *
+ * @author fanxb
+ * @date 2019/8/6 17:35
+ */
+public class CountSort {
+    /**
+     * Description:
+     *
+     * @param arr 待排序数组
+     * @return void
+     * @author fanxb
+     * @date 2019/8/6 17:36
+     */
+    public static void sort(Integer[] arr, Integer minValue, Integer maxValue) {
+        int range = maxValue - minValue + 1;
+        Integer[] numCount = new Integer[range];
+        Arrays.fill(numCount, 0);
+        for (Integer item : arr) {
+            item = item - minValue;
+            numCount[item]++;
+        }
+        int count = 0;
+        for (int i = 0; i < range; i++) {
+            if (numCount[i] == 0) {
+                continue;
+            }
+            for (int j = 0; j < numCount[i]; j++) {
+                arr[count] = minValue + i;
+                count++;
+            }
+        }
+    }
+
+
+    public static void main(String[] args) {
+        Integer[] arr = {1, 65, 32, 334, 12, 21, 65, 112, 444443};
+        sort(arr, 1, 444443);
+        System.out.println(Arrays.toString(arr));
+    }
+}
diff --git a/3.排序算法/src/sort/exchange/InsertSort.java b/3.排序算法/src/sort/exchange/InsertSort.java
index 356532f..53b99fe 100644
--- a/3.排序算法/src/sort/exchange/InsertSort.java
+++ b/3.排序算法/src/sort/exchange/InsertSort.java
@@ -18,14 +18,14 @@ public class InsertSort {
 
     public static void sort(Integer[] arr) {
         for (int i = 0, length = arr.length; i < length; i++) {
-            //有序部分从后向前比较
+            //有序部分从后向前比较,直到找到合适的位置
             int j = i, temp = arr[i];
             //如果arr[j-1]<=temp,说明arr[j]需为temp，否则将arr[j-1]向后移动一位
             for (; j > 0 && temp < arr[j - 1]; j--) {
                 arr[j] = arr[j - 1];
             }
             arr[j] = temp;
-            System.out.println("当前数组状态为："+Arrays.toString(arr));
+            System.out.println("当前数组状态为：" + Arrays.toString(arr));
         }
     }
 
diff --git a/3.排序算法/src/sort/exchange/MergeSort.java b/3.排序算法/src/sort/exchange/MergeSort.java
index 07cad2d..3680028 100644
--- a/3.排序算法/src/sort/exchange/MergeSort.java
+++ b/3.排序算法/src/sort/exchange/MergeSort.java
@@ -1,6 +1,7 @@
 package sort.exchange;
 
 import java.util.ArrayList;
+import java.util.Arrays;
 
 /**
  * 类功能简述：归并排序
@@ -13,13 +14,25 @@ import java.util.ArrayList;
  */
 public class MergeSort {
 
+    /**
+     * Description:
+     *
+     * @param arr   待排序数组
+     * @param start 开始下标
+     * @param end   结束下标
+     * @author fanxb
+     * @date 2019/8/6 9:29
+     */
     public static void mergeSort(Integer[] arr, int start, int end) {
         if (start >= end) {
             return;
         }
         int half = (start + end) / 2;
+        //归并左边
         mergeSort(arr, start, half);
+        //归并右边
         mergeSort(arr, half + 1, end);
+        //合并
         merge(arr, start, half, end);
     }
 
@@ -50,19 +63,23 @@ public class MergeSort {
                 j++;
             }
         } else {
-            //说明第二个数组卖完了，将第二个数组剩余部分放到tempList中
-            while (j <= half) {
+            //说明第二个数组已经完了，将第一个数组剩余部分放到tempList中
+            while (i <= half) {
                 //说明第二个数组处理完了
-                tempList.add(arr[j]);
-                j++;
+                tempList.add(arr[i]);
+                i++;
             }
         }
-
+        //最后将tempList复制到arr中
+        for (int k = 0, length = tempList.size(); k < length; k++) {
+            arr[start + k] = tempList.get(k);
+        }
 
     }
 
     public static void main(String[] args) {
-        Integer[] arr = {4, 3, 1, 2, 5, 4, 2, 54};
-        mergeSort(arr, 0, arr.length);
+        Integer[] arr = {4, 3, 1, 2, 5, 4, 2};
+        mergeSort(arr, 0, arr.length - 1);
+        System.out.println(Arrays.toString(arr));
     }
 }
diff --git a/3.排序算法/src/sort/exchange/RadixSort.java b/3.排序算法/src/sort/exchange/RadixSort.java
new file mode 100644
index 0000000..9dedd6a
--- /dev/null
+++ b/3.排序算法/src/sort/exchange/RadixSort.java
@@ -0,0 +1,58 @@
+package sort.exchange;
+
+import java.util.Arrays;
+import java.util.LinkedList;
+
+/**
+ * 类功能简述：基数排序
+ * 类功能详述：
+ *
+ * @author fanxb
+ * @date 2019/8/6 14:33
+ */
+public class RadixSort {
+
+    @SuppressWarnings("unchecked")
+    public static void sort(Integer[] arr) {
+        //定义桶
+        LinkedList<Integer>[] buckets = new LinkedList[10];
+        for (int i = 0; i < 10; i++) {
+            buckets[i] = new LinkedList<>();
+        }
+        int size = arr.length;
+        //当前处理第几位的数
+        int count = 0;
+        while (true) {
+            //是否继续进位
+            boolean isContinue = false;
+            //将数放到桶中
+            for (int i = 0; i < size; i++) {
+                int temp = arr[i] / (int) Math.pow(10, count) % 10;
+                if (!isContinue && temp != 0) {
+                    // 如果存在一个数取的值不为0，说明还要继续循环。
+                    isContinue = true;
+                }
+                buckets[temp].addLast(arr[i]);
+            }
+            if (!isContinue) {
+                return;
+            }
+            //从桶中取出放到arr中,注意以什么顺序放进去的就要以什么顺序取出来（先进先出）
+            int index = 0;
+            for (int i = 0; i < 10; i++) {
+                Integer item;
+                while ((item = buckets[i].pollFirst()) != null) {
+                    arr[index++] = item;
+                }
+            }
+            //位数+1
+            count++;
+        }
+    }
+
+    public static void main(String[] args) {
+        Integer[] arr = {4, 31, 1, 29, 5, 4, 2};
+        sort(arr);
+        System.out.println(Arrays.toString(arr));
+    }
+}
diff --git a/3.排序算法/src/sort/exchange/ShellSort.java b/3.排序算法/src/sort/exchange/ShellSort.java
index 7786826..125795f 100644
--- a/3.排序算法/src/sort/exchange/ShellSort.java
+++ b/3.排序算法/src/sort/exchange/ShellSort.java
@@ -34,7 +34,7 @@ public class ShellSort {
                 }
             }
             n1 /= 2;
-        } while (n1 > 0);
+        } while (n1 >= 1);
     }
 
     public static void main(String[] args) {
diff --git a/3.排序算法/src/sort/exchange/SimpleSelectSort.java b/3.排序算法/src/sort/exchange/SimpleSelectSort.java
index ed7e462..01cf089 100644
--- a/3.排序算法/src/sort/exchange/SimpleSelectSort.java
+++ b/3.排序算法/src/sort/exchange/SimpleSelectSort.java
@@ -30,7 +30,7 @@ public class SimpleSelectSort {
 
     public static void main(String[] args) {
         Integer[] arr = {1, 65, 32, 12, 21};
-        ShellSort.sort(arr);
+        sort(arr);
         System.out.println(Arrays.toString(arr));
     }
 }