# 1764. Form Array by Concatenating Subarrays of Another Array ## Description You are given a 2D integer array `groups` of length `n`. You are also given an integer array `nums`. You are asked if you can choose `n` **disjoint** subarrays from the array `nums` such that the `ith` subarray is equal to `groups[i]` (**0-indexed**), and if `i > 0`, the `(i-1)th` subarray appears **before** the `ith` subarray in `nums` (i.e. the subarrays must be in the same order as `groups`). Return `true` *if you can do this task, and* `false` *otherwise*. Note that the subarrays are **disjoint** if and only if there is no index `k` such that `nums[k]` belongs to more than one subarray. A subarray is a contiguous sequence of elements within an array. **Example 1:** ``` **Input:** groups = [[1,-1,-1],[3,-2,0]], nums = [1,-1,0,1,-1,-1,3,-2,0] **Output:** true **Explanation:** You can choose the 0th subarray as [1,-1,0,**1,-1,-1**,3,-2,0] and the 1st one as [1,-1,0,1,-1,-1,**3,-2,0**]. These subarrays are disjoint as they share no common nums[k] element. ``` **Example 2:** ``` **Input:** groups = [[10,-2],[1,2,3,4]], nums = [1,2,3,4,10,-2] **Output:** false **Explanation:** Note that choosing the subarrays [**1,2,3,4**,10,-2] and [1,2,3,4,**10,-2**] is incorrect because they are not in the same order as in groups. [10,-2] must come before [1,2,3,4]. ``` **Example 3:** ``` **Input:** groups = [[1,2,3],[3,4]], nums = [7,7,1,2,3,4,7,7] **Output:** false **Explanation:** Note that choosing the subarrays [7,7,**1,2,3**,4,7,7] and [7,7,1,2,**3,4**,7,7] is invalid because they are not disjoint. They share a common elements nums[4] (0-indexed). ``` **Constraints:** * `groups.length == n` * `1 <= n <= 103` * `1 <= groups[i].length, sum(groups[i].length) <= 103` * `1 <= nums.length <= 103` * `-107 <= groups[i][j], nums[k] <= 107` ## ac ```java ```