添加（0844.比较含退格的字符串.md）：增加typescript版本

Author: xiaofei-2020

problems/0844.比较含退格的字符串.md

@@ -399,6 +399,71 @@ var backspaceCompare = function(s, t) {
 
 ```
 
+### TypeScript
+
+> 双栈法：
+
+```typescript
+function backspaceCompare(s: string, t: string): boolean {
+    const stack1: string[] = [],
+        stack2: string[] = [];
+    for (let c of s) {
+        if (c === '#') {
+            stack1.pop();
+        } else {
+            stack1.push(c);
+        }
+    }
+    for (let c of t) {
+        if (c === '#') {
+            stack2.pop();
+        } else {
+            stack2.push(c);
+        }
+    }
+    if (stack1.length !== stack2.length) return false;
+    for (let i = 0, length = stack1.length; i < length; i++) {
+        if (stack1[i] !== stack2[i]) return false;
+    }
+    return true;
+};
+```
+
+> 双指针法：
+
+```typescript
+function backspaceCompare(s: string, t: string): boolean {
+    let sIndex: number = s.length - 1,
+        tIndex: number = t.length - 1;
+    while (true) {
+        sIndex = getIndexAfterDel(s, sIndex);
+        tIndex = getIndexAfterDel(t, tIndex);
+        if (sIndex < 0 || tIndex < 0) break;
+        if (s[sIndex] !== t[tIndex]) return false;
+        sIndex--;
+        tIndex--;
+    }
+    return sIndex === -1 && tIndex === -1;
+};
+function getIndexAfterDel(s: string, startIndex: number): number {
+    let backspaceNum: number = 0;
+    while (startIndex >= 0) {
+        // 不可消除
+        if (s[startIndex] !== '#' && backspaceNum === 0) break;
+        // 可消除
+        if (s[startIndex] === '#') {
+            backspaceNum++;
+        } else {
+            backspaceNum--;
+        }
+        startIndex--;
+    }
+    return startIndex;
+}
+```
+
+
+
 
 -----------------------
 <div align="center"><img src=https://code-thinking.cdn.bcebos.com/pics/01二维码一.jpg width=500> </img></div>