Merge pull request #1198 from xiaofei-2020/back18

添加（回溯算法去重问题的另一种写法.md）：增加typescript版本

problems/回溯算法去重问题的另一种写法.md

@@ -365,6 +365,87 @@ class Solution:
         return res
 ```
 
+TypeScript：
+
+**90.子集II**
+
+```typescript
+function subsetsWithDup(nums: number[]): number[][] {
+    nums.sort((a, b) => a - b);
+    const resArr: number[][] = [];
+    backTraking(nums, 0, []);
+    return resArr;
+    function backTraking(nums: number[], startIndex: number, route: number[]): void {
+        resArr.push(route.slice());
+        const helperSet: Set<number> = new Set();
+        for (let i = startIndex, length = nums.length; i < length; i++) {
+            if (helperSet.has(nums[i])) continue;
+            helperSet.add(nums[i]);
+            route.push(nums[i]);
+            backTraking(nums, i + 1, route);
+            route.pop();
+        }
+    }
+};
+```
+
+**40. 组合总和 II**
+
+```typescript
+function combinationSum2(candidates: number[], target: number): number[][] {
+    candidates.sort((a, b) => a - b);
+    const resArr: number[][] = [];
+    backTracking(candidates, target, 0, 0, []);
+    return resArr;
+    function backTracking(
+        candidates: number[], target: number,
+        curSum: number, startIndex: number, route: number[]
+    ) {
+        if (curSum > target) return;
+        if (curSum === target) {
+            resArr.push(route.slice());
+            return;
+        }
+        const helperSet: Set<number> = new Set();
+        for (let i = startIndex, length = candidates.length; i < length; i++) {
+            let tempVal: number = candidates[i];
+            if (helperSet.has(tempVal)) continue;
+            helperSet.add(tempVal);
+            route.push(tempVal);
+            backTracking(candidates, target, curSum + tempVal, i + 1, route);
+            route.pop();
+
+        }
+    }
+};
+```
+
+**47. 全排列 II**
+
+```typescript
+function permuteUnique(nums: number[]): number[][] {
+    const resArr: number[][] = [];
+    const usedArr: boolean[] = [];
+    backTracking(nums, []);
+    return resArr;
+    function backTracking(nums: number[], route: number[]): void {
+        if (nums.length === route.length) {
+            resArr.push(route.slice());
+            return;
+        }
+        const usedSet: Set<number> = new Set();
+        for (let i = 0, length = nums.length; i < length; i++) {
+            if (usedArr[i] === true || usedSet.has(nums[i])) continue;
+            usedSet.add(nums[i]);
+            route.push(nums[i]);
+            usedArr[i] = true;
+            backTracking(nums, route);
+            usedArr[i] = false;
+            route.pop();
+        }
+    }
+};
+```
 
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