feat: add typescript solution to lc problem: No.0409.Longest Palindrome (#581)

Author: zhaocchen

solution/0400-0499/0409.Longest Palindrome/README.md

@@ -70,6 +70,24 @@ class Solution {
 }
 ```
 
+### **TypeScript**
+
+```ts
+function longestPalindrome(s: string): number {
+    let n = s.length;
+    let ans = 0;
+    let record = new Array(128).fill(0);
+    for (let i = 0; i < n; i++) {
+        record[s.charCodeAt(i)]++;
+    }
+    for (let i = 65; i < 128; i++) {
+        let count = record[i];
+        ans += (count % 2 == 0 ? count : count - 1);
+    }
+    return ans < s.length ? ans + 1 : ans;
+};
+```
+
 ### **...**
 
 ```

solution/0400-0499/0409.Longest Palindrome/README_EN.md

@@ -78,6 +78,24 @@ class Solution {
 }
 ```
 
+### **TypeScript**
+
+```ts
+function longestPalindrome(s: string): number {
+    let n = s.length;
+    let ans = 0;
+    let record = new Array(128).fill(0);
+    for (let i = 0; i < n; i++) {
+        record[s.charCodeAt(i)]++;
+    }
+    for (let i = 65; i < 128; i++) {
+        let count = record[i];
+        ans += (count % 2 == 0 ? count : count - 1);
+    }
+    return ans < s.length ? ans + 1 : ans;
+};
+```
+
 ### **...**
 
 ```

solution/0400-0499/0409.Longest Palindrome/Solution.ts

@@ -0,0 +1,13 @@
+function longestPalindrome(s: string): number {
+    let n = s.length;
+    let ans = 0;
+    let record = new Array(128).fill(0);
+    for (let i = 0; i < n; i++) {
+        record[s.charCodeAt(i)]++;
+    }
+    for (let i = 65; i < 128; i++) {
+        let count = record[i];
+        ans += (count % 2 == 0 ? count : count - 1);
+    }
+    return ans < s.length ? ans + 1 : ans;
+};