diff --git a/budd-common/src/main/java/io/github/ehlxr/algorithm/search/BinarySearch.java b/budd-common/src/main/java/io/github/ehlxr/algorithm/search/BinarySearch.java
index 52ca52e..ff9ae2f 100644
--- a/budd-common/src/main/java/io/github/ehlxr/algorithm/search/BinarySearch.java
+++ b/budd-common/src/main/java/io/github/ehlxr/algorithm/search/BinarySearch.java
@@ -35,6 +35,12 @@ public class BinarySearch {
         System.out.println(searchRec(a, a.length, 3));
         a = new int[]{1, 2, 2, 2, 2, 5, 6, 7, 8, 9};
         System.out.println(searchFirst(a, a.length, 2));
+        a = new int[]{1, 3, 4, 5, 6, 8, 8, 8, 9};
+        System.out.println(searchLast(a, a.length, 8));
+        a = new int[]{1, 2, 2, 3, 4, 5, 6, 7, 8, 8, 9};
+        System.out.println(searchFirstGreater(a, a.length, 7));
+        a = new int[]{1, 2, 3, 4, 5, 6, 8, 9};
+        System.out.println(searchLastLess(a, a.length, 7));
     }
 
     /**
@@ -49,12 +55,10 @@ public class BinarySearch {
         int low = 0;
         int high = n - 1;
         while (low <= high) {
-            int mid = low + (high - low) >> 1;
+            int mid = low + ((high - low) >> 1);
             if (a[mid] == v) {
                 return mid;
-            }
-
-            if (a[mid] < v) {
+            } else if (a[mid] < v) {
                 low = mid + 1;
             } else {
                 high = mid - 1;
@@ -83,12 +87,10 @@ public class BinarySearch {
             return -1;
         }
 
-        int mid = low + (high - low) >> 1;
+        int mid = low + ((high - low) >> 1);
         if (a[mid] == v) {
             return mid;
-        }
-
-        if (a[mid] < v) {
+        } else if (a[mid] < v) {
             return searchRec(a, mid + 1, high, v);
         } else {
             return searchRec(a, low, mid - 1, v);
@@ -107,16 +109,14 @@ public class BinarySearch {
         int low = 0;
         int high = n - 1;
         while (low <= high) {
-            int mid = low + (high - low) >> 1;
+            int mid = low + ((high - low) >> 1);
             if (a[mid] == v) {
-                if (a[mid - 1] != v) {
+                if (mid == 0 || a[mid - 1] != v) {
                     return mid;
                 } else {
                     high = mid - 1;
                 }
-            }
-
-            if (a[mid] < v) {
+            } else if (a[mid] < v) {
                 low = mid + 1;
             } else {
                 high = mid - 1;
@@ -124,4 +124,84 @@ public class BinarySearch {
         }
         return -1;
     }
+
+    /**
+     * 查找最后一个值等于给定值的元素
+     *
+     * @param a 要查找的数组
+     * @param n 数组的长度
+     * @param v 要查找的值
+     * @return 要查找值在数组中的索引
+     */
+    public static int searchLast(int[] a, int n, int v) {
+        int low = 0;
+        int high = n - 1;
+        while (low <= high) {
+            int mid = low + ((high - low) >> 1);
+            if (a[mid] == v) {
+                if (mid == n - 1 || a[mid + 1] != v) {
+                    return mid;
+                } else {
+                    low = mid + 1;
+                }
+            } else if (a[mid] < v) {
+                low = mid + 1;
+            } else {
+                high = mid - 1;
+            }
+        }
+        return -1;
+    }
+
+    /**
+     * 查找第一个大于等于给定值的元素
+     *
+     * @param a 要查找的数组
+     * @param n 数组的长度
+     * @param v 要查找的值
+     * @return 要查找值在数组中的索引
+     */
+    public static int searchFirstGreater(int[] a, int n, int v) {
+        int low = 0;
+        int high = n - 1;
+        while (low <= high) {
+            int mid = low + ((high - low) >> 1);
+            if (a[mid] < v) {
+                low = mid + 1;
+            } else {
+                if (mid == 0 || a[mid - 1] < v) {
+                    return mid;
+                } else {
+                    high = mid - 1;
+                }
+            }
+        }
+        return -1;
+    }
+
+    /**
+     * 查找最后一个小于等于给定值的元素
+     *
+     * @param a 要查找的数组
+     * @param n 数组的长度
+     * @param v 要查找的值
+     * @return 要查找值在数组中的索引
+     */
+    public static int searchLastLess(int[] a, int n, int v) {
+        int low = 0;
+        int high = n - 1;
+        while (low <= high) {
+            int mid = low + ((high - low) >> 1);
+            if (a[mid] > v) {
+                high = mid - 1;
+            } else {
+                if (mid == n - 1 || a[mid + 1] > v) {
+                    return mid;
+                } else {
+                    low = mid + 1;
+                }
+            }
+        }
+        return -1;
+    }
 }