Check Array Formation Through Concatenation

Problem Statement

You are given an array of distinct integers arr and an array of integer arrays pieces, where the integers in pieces are distinct. Your goal is to form arr by concatenating the arrays in pieces in any order. However, you are not allowed to reorder the integers in each array pieces[i].

Return true if it is possible to form the array arr from pieces. Otherwise, return false.

Example 1:

Input: arr = [85], pieces = [[85]]
Output: true

Example 2:

Input: arr = [15,88], pieces = [[88],[15]]
Output: true
Explanation: Concatenate [15] then [88]

Example 3:

Input: arr = [49,18,16], pieces = [[16,18,49]]
Output: false
Explanation: Even though the numbers match, we cannot reorder pieces[0].

Example 4:

Input: arr = [91,4,64,78], pieces = [[78],[4,64],[91]]
Output: true
Explanation: Concatenate [91] then [4,64] then [78]

Example 5:

Input: arr = [1,3,5,7], pieces = [[2,4,6,8]]
Output: false


  • 1 <= pieces.length <= arr.length <= 100

Solution Using C# Dictionary -


Step 1: Initialize a Dictionary mapping to record piece’s first integer and the whole piece array.
Step 2: Initialize an index i to record the current matching index in arr.
Step 3: Find the piece starting with arr[i] in mapping. Return false if no match.
Step 4: Use the matched piece to match piece[] sublist starting from i with the same length. Return false if any integer is different.
Step 5: Increment the index i.
Step 6: Repeat until i reach the end of arr. Return true.

Complexity Analysis :

  • Time Complexity: O(N).
solution using Dictionary

Using no extra space -

solution using no extra space

Github link :

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