feat: add solutions to lc problem: No.2981

solution/2900-2999/2981.Find Longest Special Substring That Occurs Thrice I/README.md

@@ -269,4 +269,86 @@ function maximumLength(s: string): number {
 
 <!-- solution:end -->
 
+<!-- solution:start -->
+
+### 方法二：计数
+
+时间复杂度 $O(n)$。
+
+<!-- tabs:start -->
+
+#### TypeScript
+
+```ts
+function maximumLength(s: string): number {
+    const cnt = new Map<string, number>();
+    const n = s.length;
+    let [c, ch] = [0, ''];
+
+    for (let i = 0; i < n + 1; i++) {
+        if (ch === s[i]) {
+            c++;
+        } else {
+            let j = 1;
+            while (c) {
+                const char = ch.repeat(j++);
+                cnt.set(char, (cnt.get(char) ?? 0) + c);
+                c--;
+            }
+
+            ch = s[i];
+            c = 1;
+        }
+    }
+
+    let res = -1;
+    for (const [x, c] of cnt) {
+        if (c >= 3) {
+            res = Math.max(res, x.length);
+        }
+    }
+
+    return res;
+}
+```
+
+### JavaScript
+
+```js
+function maximumLength(s) {
+    const cnt = new Map();
+    const n = s.length;
+    let [c, ch] = [0, ''];
+
+    for (let i = 0; i < n + 1; i++) {
+        if (ch === s[i]) {
+            c++;
+        } else {
+            let j = 1;
+            while (c) {
+                const char = ch.repeat(j++);
+                cnt.set(char, (cnt.get(char) ?? 0) + c);
+                c--;
+            }
+
+            ch = s[i];
+            c = 1;
+        }
+    }
+
+    let res = -1;
+    for (const [x, c] of cnt) {
+        if (c >= 3) {
+            res = Math.max(res, x.length);
+        }
+    }
+
+    return res;
+}
+```
+
+<!-- tabs:end -->
+
+<!-- solution:end -->
+
 <!-- problem:end -->

solution/2900-2999/2981.Find Longest Special Substring That Occurs Thrice I/README_EN.md

@@ -267,4 +267,86 @@ function maximumLength(s: string): number {
 
 <!-- solution:end -->
 
+<!-- solution:start -->
+
+### Solution 2: Counting
+
+The time complexity is $O(n)$
+
+<!-- tabs:start -->
+
+#### TypeScript
+
+```ts
+function maximumLength(s: string): number {
+    const cnt = new Map<string, number>();
+    const n = s.length;
+    let [c, ch] = [0, ''];
+
+    for (let i = 0; i < n + 1; i++) {
+        if (ch === s[i]) {
+            c++;
+        } else {
+            let j = 1;
+            while (c) {
+                const char = ch.repeat(j++);
+                cnt.set(char, (cnt.get(char) ?? 0) + c);
+                c--;
+            }
+
+            ch = s[i];
+            c = 1;
+        }
+    }
+
+    let res = -1;
+    for (const [x, c] of cnt) {
+        if (c >= 3) {
+            res = Math.max(res, x.length);
+        }
+    }
+
+    return res;
+}
+```
+
+### JavaScript
+
+```js
+function maximumLength(s) {
+    const cnt = new Map();
+    const n = s.length;
+    let [c, ch] = [0, ''];
+
+    for (let i = 0; i < n + 1; i++) {
+        if (ch === s[i]) {
+            c++;
+        } else {
+            let j = 1;
+            while (c) {
+                const char = ch.repeat(j++);
+                cnt.set(char, (cnt.get(char) ?? 0) + c);
+                c--;
+            }
+
+            ch = s[i];
+            c = 1;
+        }
+    }
+
+    let res = -1;
+    for (const [x, c] of cnt) {
+        if (c >= 3) {
+            res = Math.max(res, x.length);
+        }
+    }
+
+    return res;
+}
+```
+
+<!-- tabs:end -->
+
+<!-- solution:end -->
+
 <!-- problem:end -->

solution/2900-2999/2981.Find Longest Special Substring That Occurs Thrice I/Solution2.js

@@ -0,0 +1,30 @@
+function maximumLength(s) {
+    const cnt = new Map();
+    const n = s.length;
+    let [c, ch] = [0, ''];
+
+    for (let i = 0; i < n + 1; i++) {
+        if (ch === s[i]) {
+            c++;
+        } else {
+            let j = 1;
+            while (c) {
+                const char = ch.repeat(j++);
+                cnt.set(char, (cnt.get(char) ?? 0) + c);
+                c--;
+            }
+
+            ch = s[i];
+            c = 1;
+        }
+    }
+
+    let res = -1;
+    for (const [x, c] of cnt) {
+        if (c >= 3) {
+            res = Math.max(res, x.length);
+        }
+    }
+
+    return res;
+}

solution/2900-2999/2981.Find Longest Special Substring That Occurs Thrice I/Solution2.ts

@@ -0,0 +1,30 @@
+function maximumLength(s: string): number {
+    const cnt = new Map<string, number>();
+    const n = s.length;
+    let [c, ch] = [0, ''];
+
+    for (let i = 0; i < n + 1; i++) {
+        if (ch === s[i]) {
+            c++;
+        } else {
+            let j = 1;
+            while (c) {
+                const char = ch.repeat(j++);
+                cnt.set(char, (cnt.get(char) ?? 0) + c);
+                c--;
+            }
+
+            ch = s[i];
+            c = 1;
+        }
+    }
+
+    let res = -1;
+    for (const [x, c] of cnt) {
+        if (c >= 3) {
+            res = Math.max(res, x.length);
+        }
+    }
+
+    return res;
+}