feat: add solutions to lc problems: No.2630,2631

* No.2630.Memoize II
* No.2631.Group By

Author: yanglbme

solution/2600-2699/2630.Memoize II/README.md

@@ -69,14 +69,45 @@ fn = function (a, b) { return ({...a, ...b}); }
 
 <!-- 这里可写通用的实现逻辑 -->
 
+**方法一：哈希表**
+
+我们用哈希表 $cache$ 记录函数调用的结果，其中键为函数参数，值为函数返回值。当函数被调用时，先将参数转换为字符串作为键，然后在 $cache$ 中查找，如果找到则直接返回，否则调用函数并将结果存入 $cache$ 中。
+
+时间复杂度 $O(1)$，空间复杂度 $O(n)$，其中 $n$ 为函数调用的次数。
+
 <!-- tabs:start -->
 
 ### **TypeScript**
 
 <!-- 这里可写当前语言的特殊实现逻辑 -->
 
 ```ts
+type Fn = (...params: any) => any;
+
+function memoize(fn: Fn): Fn {
+    const cache: Map<string, any> = new Map();
+
+    return function (...args) {
+        const key = args.join('-');
+        if (cache.has(key)) {
+            return cache.get(key);
+        }
+        const ans = fn.apply(this, args);
+        cache.set(key, ans);
+        return ans;
+    };
+}
 
+/**
+ * let callCount = 0;
+ * const memoizedFn = memoize(function (a, b) {
+ *	 callCount += 1;
+ *   return a + b;
+ * })
+ * memoizedFn(2, 3) // 5
+ * memoizedFn(2, 3) // 5
+ * console.log(callCount) // 1
+ */
 ```
 
 ### **...**

solution/2600-2699/2630.Memoize II/README_EN.md

@@ -68,7 +68,32 @@ Merging two empty objects will always result in an empty object. The 2nd and 3rd
 ### **TypeScript**
 
 ```ts
+type Fn = (...params: any) => any;
+
+function memoize(fn: Fn): Fn {
+    const cache: Map<string, any> = new Map();
+
+    return function (...args) {
+        const key = args.join('-');
+        if (cache.has(key)) {
+            return cache.get(key);
+        }
+        const ans = fn.apply(this, args);
+        cache.set(key, ans);
+        return ans;
+    };
+}
 
+/**
+ * let callCount = 0;
+ * const memoizedFn = memoize(function (a, b) {
+ *	 callCount += 1;
+ *   return a + b;
+ * })
+ * memoizedFn(2, 3) // 5
+ * memoizedFn(2, 3) // 5
+ * console.log(callCount) // 1
+ */
 ```
 
 ### **...**

solution/2600-2699/2630.Memoize II/Solution.ts

@@ -0,0 +1,26 @@
+type Fn = (...params: any) => any;
+
+function memoize(fn: Fn): Fn {
+    const cache: Map<string, any> = new Map();
+
+    return function (...args) {
+        const key = args.join('-');
+        if (cache.has(key)) {
+            return cache.get(key);
+        }
+        const ans = fn.apply(this, args);
+        cache.set(key, ans);
+        return ans;
+    };
+}
+
+/**
+ * let callCount = 0;
+ * const memoizedFn = memoize(function (a, b) {
+ *	 callCount += 1;
+ *   return a + b;
+ * })
+ * memoizedFn(2, 3) // 5
+ * memoizedFn(2, 3) // 5
+ * console.log(callCount) // 1
+ */

solution/2600-2699/2631.Group By/README.md

@@ -103,7 +103,27 @@ fn = function (n) {
 <!-- 这里可写当前语言的特殊实现逻辑 -->
 
 ```ts
+declare global {
+    interface Array<T> {
+        groupBy(fn: (item: T) => string): Record<string, T[]>;
+    }
+}
 
+Array.prototype.groupBy = function (fn) {
+    return this.reduce((acc, item) => {
+        const key = fn(item);
+        if (acc[key]) {
+            acc[key].push(item);
+        } else {
+            acc[key] = [item];
+        }
+        return acc;
+    }, {});
+};
+
+/**
+ * [1,2,3].groupBy(String) // {"1":[1],"2":[2],"3":[3]}
+ */
 ```
 
 ### **...**

solution/2600-2699/2631.Group By/README_EN.md

@@ -95,7 +95,27 @@ The selector function splits the array by whether each number is greater than 5.
 ### **TypeScript**
 
 ```ts
+declare global {
+    interface Array<T> {
+        groupBy(fn: (item: T) => string): Record<string, T[]>;
+    }
+}
 
+Array.prototype.groupBy = function (fn) {
+    return this.reduce((acc, item) => {
+        const key = fn(item);
+        if (acc[key]) {
+            acc[key].push(item);
+        } else {
+            acc[key] = [item];
+        }
+        return acc;
+    }, {});
+};
+
+/**
+ * [1,2,3].groupBy(String) // {"1":[1],"2":[2],"3":[3]}
+ */
 ```
 
 ### **...**

solution/2600-2699/2631.Group By/Solution.ts

@@ -0,0 +1,21 @@
+declare global {
+    interface Array<T> {
+        groupBy(fn: (item: T) => string): Record<string, T[]>;
+    }
+}
+
+Array.prototype.groupBy = function (fn) {
+    return this.reduce((acc, item) => {
+        const key = fn(item);
+        if (acc[key]) {
+            acc[key].push(item);
+        } else {
+            acc[key] = [item];
+        }
+        return acc;
+    }, {});
+};
+
+/**
+ * [1,2,3].groupBy(String) // {"1":[1],"2":[2],"3":[3]}
+ */