添加（0205.同构字符串.md）：增加typescript版本

Author: xiaofei-2020

problems/0205.同构字符串.md

@@ -156,6 +156,28 @@ var isIsomorphic = function(s, t) {
 };
 ```
 
+## TypeScript
+
+```typescript
+function isIsomorphic(s: string, t: string): boolean {
+    const helperMap1: Map<string, string> = new Map();
+    const helperMap2: Map<string, string> = new Map();
+    for (let i = 0, length = s.length; i < length; i++) {
+        let temp1: string | undefined = helperMap1.get(s[i]);
+        let temp2: string | undefined = helperMap2.get(t[i]);
+        if (temp1 === undefined && temp2 === undefined) {
+            helperMap1.set(s[i], t[i]);
+            helperMap2.set(t[i], s[i]);
+        } else if (temp1 !== t[i] || temp2 !== s[i]) {
+            return false;
+        }
+    }
+    return true;
+};
+```
+
+
+
 
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