diff --git a/solution/0300-0399/0379.Design Phone Directory/README.md b/solution/0300-0399/0379.Design Phone Directory/README.md
index f553a7940cdf3..1b671e581f3d3 100644
--- a/solution/0300-0399/0379.Design Phone Directory/README.md	
+++ b/solution/0300-0399/0379.Design Phone Directory/README.md	
@@ -73,7 +73,17 @@ directory.check(2);
 
 <!-- solution:start -->
 
-### 方法一
+### 方法一：哈希表
+
+我们可以使用一个哈希集合 `available` 来存储未被分配的电话号码，初始时，哈希表中存储的是 `[0, 1, 2, ..., maxNumbers - 1]`。
+
+调用 `get` 方法时，我们从 `available` 中取出一个未被分配的电话号码，如果 `available` 为空，则返回 `-1`。时间复杂度 $O(1)$。
+
+调用 `check` 方法时，我们只需要判断 `number` 是否在 `available` 中即可。时间复杂度 $O(1)$。
+
+调用 `release` 方法时，我们将 `number` 添加到 `available` 中。时间复杂度 $O(1)$。
+
+空间复杂度 $O(n)$，其中 $n$ 是 `maxNumbers` 的值。
 
 <!-- tabs:start -->
 
@@ -81,35 +91,20 @@ directory.check(2);
 
 ```python
 class PhoneDirectory:
+
     def __init__(self, maxNumbers: int):
-        """
-        Initialize your data structure here
-        @param maxNumbers - The maximum numbers that can be stored in the phone directory.
-        """
-        self.provided = [False] * maxNumbers
+        self.available = set(range(maxNumbers))
 
     def get(self) -> int:
-        """
-        Provide a number which is not assigned to anyone.
-        @return - Return an available number. Return -1 if none is available.
-        """
-        for i in range(len(self.provided)):
-            if not self.provided[i]:
-                self.provided[i] = True
-                return i
-        return -1
+        if not self.available:
+            return -1
+        return self.available.pop()
 
     def check(self, number: int) -> bool:
-        """
-        Check if a number is available or not.
-        """
-        return not self.provided[number]
+        return number in self.available
 
     def release(self, number: int) -> None:
-        """
-        Recycle or release a number.
-        """
-        self.provided[number] = False
+        self.available.add(number)
 
 
 # Your PhoneDirectory object will be instantiated and called as such:
@@ -123,39 +118,29 @@ class PhoneDirectory:
 
 ```java
 class PhoneDirectory {
+    private Set<Integer> available = new HashSet<>();
 
-    private boolean[] provided;
-
-    /**
-       Initialize your data structure here
-        @param maxNumbers - The maximum numbers that can be stored in the phone directory.
-     */
     public PhoneDirectory(int maxNumbers) {
-        provided = new boolean[maxNumbers];
+        for (int i = 0; i < maxNumbers; ++i) {
+            available.add(i);
+        }
     }
 
-    /**
-       Provide a number which is not assigned to anyone.
-        @return - Return an available number. Return -1 if none is available.
-     */
     public int get() {
-        for (int i = 0; i < provided.length; ++i) {
-            if (!provided[i]) {
-                provided[i] = true;
-                return i;
-            }
+        if (available.isEmpty()) {
+            return -1;
         }
-        return -1;
+        int x = available.iterator().next();
+        available.remove(x);
+        return x;
     }
 
-    /** Check if a number is available or not. */
     public boolean check(int number) {
-        return !provided[number];
+        return available.contains(number);
     }
 
-    /** Recycle or release a number. */
     public void release(int number) {
-        provided[number] = false;
+        available.add(number);
     }
 }
 
@@ -168,6 +153,127 @@ class PhoneDirectory {
  */
 ```
 
+#### C++
+
+```cpp
+class PhoneDirectory {
+public:
+    PhoneDirectory(int maxNumbers) {
+        for (int i = 0; i < maxNumbers; ++i) {
+            available.insert(i);
+        }
+    }
+
+    int get() {
+        if (available.empty()) {
+            return -1;
+        }
+        int x = *available.begin();
+        available.erase(x);
+        return x;
+    }
+
+    bool check(int number) {
+        return available.contains(number);
+    }
+
+    void release(int number) {
+        available.insert(number);
+    }
+
+private:
+    unordered_set<int> available;
+};
+
+/**
+ * Your PhoneDirectory object will be instantiated and called as such:
+ * PhoneDirectory* obj = new PhoneDirectory(maxNumbers);
+ * int param_1 = obj->get();
+ * bool param_2 = obj->check(number);
+ * obj->release(number);
+ */
+```
+
+#### Go
+
+```go
+type PhoneDirectory struct {
+	available map[int]bool
+}
+
+func Constructor(maxNumbers int) PhoneDirectory {
+	available := make(map[int]bool)
+	for i := 0; i < maxNumbers; i++ {
+		available[i] = true
+	}
+	return PhoneDirectory{available}
+}
+
+func (this *PhoneDirectory) Get() int {
+	for k := range this.available {
+		delete(this.available, k)
+		return k
+	}
+	return -1
+}
+
+func (this *PhoneDirectory) Check(number int) bool {
+	_, ok := this.available[number]
+	return ok
+}
+
+func (this *PhoneDirectory) Release(number int) {
+	this.available[number] = true
+}
+
+/**
+ * Your PhoneDirectory object will be instantiated and called as such:
+ * obj := Constructor(maxNumbers);
+ * param_1 := obj.Get();
+ * param_2 := obj.Check(number);
+ * obj.Release(number);
+ */
+```
+
+#### TypeScript
+
+```ts
+class PhoneDirectory {
+    private available: Set<number> = new Set();
+
+    constructor(maxNumbers: number) {
+        for (let i = 0; i < maxNumbers; ++i) {
+            this.available.add(i);
+        }
+    }
+
+    get(): number {
+        const [x] = this.available;
+        if (x === undefined) {
+            return -1;
+        }
+        this.available.delete(x);
+        return x;
+    }
+
+    check(number: number): boolean {
+        return this.available.has(number);
+    }
+
+    release(number: number): void {
+        this.available.add(number);
+    }
+}
+
+/**
+ * Your PhoneDirectory object will be instantiated and called as such:
+ * var obj = new PhoneDirectory(maxNumbers)
+ * var param_1 = obj.get()
+ * var param_2 = obj.check(number)
+ * obj.release(number)
+ */
+```
+
 <!-- tabs:end -->
 
 <!-- solution:end -->
diff --git a/solution/0300-0399/0379.Design Phone Directory/README_EN.md b/solution/0300-0399/0379.Design Phone Directory/README_EN.md
index 0e45d26b81770..bd22f9e773073 100644
--- a/solution/0300-0399/0379.Design Phone Directory/README_EN.md	
+++ b/solution/0300-0399/0379.Design Phone Directory/README_EN.md	
@@ -67,7 +67,17 @@ phoneDirectory.check(2);   // Number 2 is available again, return true.
 
 <!-- solution:start -->
 
-### Solution 1
+### Solution 1: Hash Table
+
+We can use a hash set `available` to store unallocated phone numbers. Initially, the hash set contains `[0, 1, 2, ..., maxNumbers - 1]`.
+
+When the `get` method is called, we take an unallocated phone number from `available`. If `available` is empty, we return `-1`. The time complexity is $O(1)$.
+
+When the `check` method is called, we just need to check whether `number` is in `available`. The time complexity is $O(1)$.
+
+When the `release` method is called, we add `number` to `available`. The time complexity is $O(1)$.
+
+The space complexity is $O(n)$, where $n$ is the value of `maxNumbers`.
 
 <!-- tabs:start -->
 
@@ -75,35 +85,20 @@ phoneDirectory.check(2);   // Number 2 is available again, return true.
 
 ```python
 class PhoneDirectory:
+
     def __init__(self, maxNumbers: int):
-        """
-        Initialize your data structure here
-        @param maxNumbers - The maximum numbers that can be stored in the phone directory.
-        """
-        self.provided = [False] * maxNumbers
+        self.available = set(range(maxNumbers))
 
     def get(self) -> int:
-        """
-        Provide a number which is not assigned to anyone.
-        @return - Return an available number. Return -1 if none is available.
-        """
-        for i in range(len(self.provided)):
-            if not self.provided[i]:
-                self.provided[i] = True
-                return i
-        return -1
+        if not self.available:
+            return -1
+        return self.available.pop()
 
     def check(self, number: int) -> bool:
-        """
-        Check if a number is available or not.
-        """
-        return not self.provided[number]
+        return number in self.available
 
     def release(self, number: int) -> None:
-        """
-        Recycle or release a number.
-        """
-        self.provided[number] = False
+        self.available.add(number)
 
 
 # Your PhoneDirectory object will be instantiated and called as such:
@@ -117,39 +112,29 @@ class PhoneDirectory:
 
 ```java
 class PhoneDirectory {
+    private Set<Integer> available = new HashSet<>();
 
-    private boolean[] provided;
-
-    /**
-       Initialize your data structure here
-        @param maxNumbers - The maximum numbers that can be stored in the phone directory.
-     */
     public PhoneDirectory(int maxNumbers) {
-        provided = new boolean[maxNumbers];
+        for (int i = 0; i < maxNumbers; ++i) {
+            available.add(i);
+        }
     }
 
-    /**
-       Provide a number which is not assigned to anyone.
-        @return - Return an available number. Return -1 if none is available.
-     */
     public int get() {
-        for (int i = 0; i < provided.length; ++i) {
-            if (!provided[i]) {
-                provided[i] = true;
-                return i;
-            }
+        if (available.isEmpty()) {
+            return -1;
         }
-        return -1;
+        int x = available.iterator().next();
+        available.remove(x);
+        return x;
     }
 
-    /** Check if a number is available or not. */
     public boolean check(int number) {
-        return !provided[number];
+        return available.contains(number);
     }
 
-    /** Recycle or release a number. */
     public void release(int number) {
-        provided[number] = false;
+        available.add(number);
     }
 }
 
@@ -162,6 +147,127 @@ class PhoneDirectory {
  */
 ```
 
+#### C++
+
+```cpp
+class PhoneDirectory {
+public:
+    PhoneDirectory(int maxNumbers) {
+        for (int i = 0; i < maxNumbers; ++i) {
+            available.insert(i);
+        }
+    }
+
+    int get() {
+        if (available.empty()) {
+            return -1;
+        }
+        int x = *available.begin();
+        available.erase(x);
+        return x;
+    }
+
+    bool check(int number) {
+        return available.contains(number);
+    }
+
+    void release(int number) {
+        available.insert(number);
+    }
+
+private:
+    unordered_set<int> available;
+};
+
+/**
+ * Your PhoneDirectory object will be instantiated and called as such:
+ * PhoneDirectory* obj = new PhoneDirectory(maxNumbers);
+ * int param_1 = obj->get();
+ * bool param_2 = obj->check(number);
+ * obj->release(number);
+ */
+```
+
+#### Go
+
+```go
+type PhoneDirectory struct {
+	available map[int]bool
+}
+
+func Constructor(maxNumbers int) PhoneDirectory {
+	available := make(map[int]bool)
+	for i := 0; i < maxNumbers; i++ {
+		available[i] = true
+	}
+	return PhoneDirectory{available}
+}
+
+func (this *PhoneDirectory) Get() int {
+	for k := range this.available {
+		delete(this.available, k)
+		return k
+	}
+	return -1
+}
+
+func (this *PhoneDirectory) Check(number int) bool {
+	_, ok := this.available[number]
+	return ok
+}
+
+func (this *PhoneDirectory) Release(number int) {
+	this.available[number] = true
+}
+
+/**
+ * Your PhoneDirectory object will be instantiated and called as such:
+ * obj := Constructor(maxNumbers);
+ * param_1 := obj.Get();
+ * param_2 := obj.Check(number);
+ * obj.Release(number);
+ */
+```
+
+#### TypeScript
+
+```ts
+class PhoneDirectory {
+    private available: Set<number> = new Set();
+
+    constructor(maxNumbers: number) {
+        for (let i = 0; i < maxNumbers; ++i) {
+            this.available.add(i);
+        }
+    }
+
+    get(): number {
+        const [x] = this.available;
+        if (x === undefined) {
+            return -1;
+        }
+        this.available.delete(x);
+        return x;
+    }
+
+    check(number: number): boolean {
+        return this.available.has(number);
+    }
+
+    release(number: number): void {
+        this.available.add(number);
+    }
+}
+
+/**
+ * Your PhoneDirectory object will be instantiated and called as such:
+ * var obj = new PhoneDirectory(maxNumbers)
+ * var param_1 = obj.get()
+ * var param_2 = obj.check(number)
+ * obj.release(number)
+ */
+```
+
 <!-- tabs:end -->
 
 <!-- solution:end -->
diff --git a/solution/0300-0399/0379.Design Phone Directory/Solution.cpp b/solution/0300-0399/0379.Design Phone Directory/Solution.cpp
new file mode 100644
index 0000000000000..fea0995b278c3
--- /dev/null
+++ b/solution/0300-0399/0379.Design Phone Directory/Solution.cpp	
@@ -0,0 +1,36 @@
+class PhoneDirectory {
+public:
+    PhoneDirectory(int maxNumbers) {
+        for (int i = 0; i < maxNumbers; ++i) {
+            available.insert(i);
+        }
+    }
+
+    int get() {
+        if (available.empty()) {
+            return -1;
+        }
+        int x = *available.begin();
+        available.erase(x);
+        return x;
+    }
+
+    bool check(int number) {
+        return available.contains(number);
+    }
+
+    void release(int number) {
+        available.insert(number);
+    }
+
+private:
+    unordered_set<int> available;
+};
+
+/**
+ * Your PhoneDirectory object will be instantiated and called as such:
+ * PhoneDirectory* obj = new PhoneDirectory(maxNumbers);
+ * int param_1 = obj->get();
+ * bool param_2 = obj->check(number);
+ * obj->release(number);
+ */
\ No newline at end of file
diff --git a/solution/0300-0399/0379.Design Phone Directory/Solution.go b/solution/0300-0399/0379.Design Phone Directory/Solution.go
new file mode 100644
index 0000000000000..7df5601d90a62
--- /dev/null
+++ b/solution/0300-0399/0379.Design Phone Directory/Solution.go	
@@ -0,0 +1,36 @@
+type PhoneDirectory struct {
+	available map[int]bool
+}
+
+func Constructor(maxNumbers int) PhoneDirectory {
+	available := make(map[int]bool)
+	for i := 0; i < maxNumbers; i++ {
+		available[i] = true
+	}
+	return PhoneDirectory{available}
+}
+
+func (this *PhoneDirectory) Get() int {
+	for k := range this.available {
+		delete(this.available, k)
+		return k
+	}
+	return -1
+}
+
+func (this *PhoneDirectory) Check(number int) bool {
+	_, ok := this.available[number]
+	return ok
+}
+
+func (this *PhoneDirectory) Release(number int) {
+	this.available[number] = true
+}
+
+/**
+ * Your PhoneDirectory object will be instantiated and called as such:
+ * obj := Constructor(maxNumbers);
+ * param_1 := obj.Get();
+ * param_2 := obj.Check(number);
+ * obj.Release(number);
+ */
\ No newline at end of file
diff --git a/solution/0300-0399/0379.Design Phone Directory/Solution.java b/solution/0300-0399/0379.Design Phone Directory/Solution.java
index b4afc45848139..9fcbbb41d0c45 100644
--- a/solution/0300-0399/0379.Design Phone Directory/Solution.java	
+++ b/solution/0300-0399/0379.Design Phone Directory/Solution.java	
@@ -1,37 +1,27 @@
 class PhoneDirectory {
+    private Set<Integer> available = new HashSet<>();
 
-    private boolean[] provided;
-
-    /**
-       Initialize your data structure here
-        @param maxNumbers - The maximum numbers that can be stored in the phone directory.
-     */
     public PhoneDirectory(int maxNumbers) {
-        provided = new boolean[maxNumbers];
+        for (int i = 0; i < maxNumbers; ++i) {
+            available.add(i);
+        }
     }
 
-    /**
-       Provide a number which is not assigned to anyone.
-        @return - Return an available number. Return -1 if none is available.
-     */
     public int get() {
-        for (int i = 0; i < provided.length; ++i) {
-            if (!provided[i]) {
-                provided[i] = true;
-                return i;
-            }
+        if (available.isEmpty()) {
+            return -1;
         }
-        return -1;
+        int x = available.iterator().next();
+        available.remove(x);
+        return x;
     }
 
-    /** Check if a number is available or not. */
     public boolean check(int number) {
-        return !provided[number];
+        return available.contains(number);
     }
 
-    /** Recycle or release a number. */
     public void release(int number) {
-        provided[number] = false;
+        available.add(number);
     }
 }
 
diff --git a/solution/0300-0399/0379.Design Phone Directory/Solution.py b/solution/0300-0399/0379.Design Phone Directory/Solution.py
index 47fc2dd96eda9..bf3ed3c586544 100644
--- a/solution/0300-0399/0379.Design Phone Directory/Solution.py	
+++ b/solution/0300-0399/0379.Design Phone Directory/Solution.py	
@@ -1,33 +1,18 @@
 class PhoneDirectory:
+
     def __init__(self, maxNumbers: int):
-        """
-        Initialize your data structure here
-        @param maxNumbers - The maximum numbers that can be stored in the phone directory.
-        """
-        self.provided = [False] * maxNumbers
+        self.available = set(range(maxNumbers))
 
     def get(self) -> int:
-        """
-        Provide a number which is not assigned to anyone.
-        @return - Return an available number. Return -1 if none is available.
-        """
-        for i in range(len(self.provided)):
-            if not self.provided[i]:
-                self.provided[i] = True
-                return i
-        return -1
+        if not self.available:
+            return -1
+        return self.available.pop()
 
     def check(self, number: int) -> bool:
-        """
-        Check if a number is available or not.
-        """
-        return not self.provided[number]
+        return number in self.available
 
     def release(self, number: int) -> None:
-        """
-        Recycle or release a number.
-        """
-        self.provided[number] = False
+        self.available.add(number)
 
 
 # Your PhoneDirectory object will be instantiated and called as such:
diff --git a/solution/0300-0399/0379.Design Phone Directory/Solution.ts b/solution/0300-0399/0379.Design Phone Directory/Solution.ts
new file mode 100644
index 0000000000000..06ec49e02df18
--- /dev/null
+++ b/solution/0300-0399/0379.Design Phone Directory/Solution.ts	
@@ -0,0 +1,34 @@
+class PhoneDirectory {
+    private available: Set<number> = new Set();
+
+    constructor(maxNumbers: number) {
+        for (let i = 0; i < maxNumbers; ++i) {
+            this.available.add(i);
+        }
+    }
+
+    get(): number {
+        const [x] = this.available;
+        if (x === undefined) {
+            return -1;
+        }
+        this.available.delete(x);
+        return x;
+    }
+
+    check(number: number): boolean {
+        return this.available.has(number);
+    }
+
+    release(number: number): void {
+        this.available.add(number);
+    }
+}
+
+/**
+ * Your PhoneDirectory object will be instantiated and called as such:
+ * var obj = new PhoneDirectory(maxNumbers)
+ * var param_1 = obj.get()
+ * var param_2 = obj.check(number)
+ * obj.release(number)
+ */