diff --git a/src/problem/mod.rs b/src/problem/mod.rs
index 06b2c69..f6d9852 100644
--- a/src/problem/mod.rs
+++ b/src/problem/mod.rs
@@ -462,3 +462,5 @@ mod p119_pascals_triangle_ii;
 mod p350_intersection_of_two_arrays_ii;
 
 mod p541_reverse_string_ii;
+
+mod p81_search_in_rotated_sorted_array_ii;
diff --git a/src/problem/p81_search_in_rotated_sorted_array_ii.rs b/src/problem/p81_search_in_rotated_sorted_array_ii.rs
new file mode 100644
index 0000000..8f560ac
--- /dev/null
+++ b/src/problem/p81_search_in_rotated_sorted_array_ii.rs
@@ -0,0 +1,90 @@
+/**
+ * [81] Search in Rotated Sorted Array II
+ */
+pub struct Solution {}
+
+// submission codes start here
+
+impl Solution {
+    pub fn search(nums: Vec<i32>, target: i32) -> bool {
+        if nums.len() == 1 {
+            return target == nums[0];
+        }
+
+        let (mut left, mut right) = (0, nums.len());
+
+        // 搜索范围[left, right)
+        while left < right {
+            let middle = (right - left) / 2 + left;
+
+            if nums[middle] == target {
+                return true;
+            }
+
+            if nums[middle] > nums[0] {
+                // 左侧的数组是有序的
+                if target >= nums[0] && target < nums[middle] {
+                    right = Self::get_first_middle(&nums, middle);
+                } else {
+                    left = Self::get_last_middle(&nums, middle) + 1;
+                }
+            } else if nums[middle] == nums[0] {
+                // 有可能nums[middle] == nums[0]
+                let first_middle = Self::get_first_middle(&nums, middle);
+                if first_middle == 0 {
+                    // [0, middle] 都是同一个数
+                    left = Self::get_last_middle(&nums, middle) + 1;
+                } else {
+                    // 反之那么[middle,]都是同一个数
+                    right = first_middle;
+                }
+            } else {
+                // 右侧数组是有序的
+                if target > nums[middle] && target <= nums[nums.len() - 1] {
+                    left = Self::get_last_middle(&nums, middle) + 1;
+                } else {
+                    right = Self::get_first_middle(&nums, middle);
+                }
+            }
+        }
+
+        false
+    }
+
+    fn get_first_middle(nums: &Vec<i32>, mut middle: usize) -> usize {
+        while middle > 0 && nums[middle - 1] == nums[middle] {
+            middle -= 1;
+        }
+
+        middle
+    }
+
+    fn get_last_middle(nums: &Vec<i32>, mut middle: usize) -> usize {
+        while middle < nums.len() - 1 && nums[middle + 1] == nums[middle] {
+            middle += 1;
+        }
+
+        middle
+    }
+}
+
+// submission codes end
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_81() {
+        assert!(Solution::search(
+            vec![1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1],
+            2
+        ));
+        assert!(Solution::search(
+            vec![1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1],
+            2
+        ));
+        assert!(Solution::search(vec![2, 5, 6, 0, 0, 1, 2], 0));
+        assert!(!Solution::search(vec![2, 5, 6, 0, 0, 1, 2], 3));
+    }
+}