Formatted question description: https://leetcode.ca/all/1640.html

# Question

/**

1640. Check Array Formation Through Concatenation

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 = , pieces = []
Output: true

Example 2:

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

Example 3:

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

Example 4:

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

Example 5:

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

Constraints:
1 <= pieces.length <= arr.length <= 100
sum(pieces[i].length) == arr.length
1 <= pieces[i].length <= arr.length
1 <= arr[i], pieces[i][j] <= 100
The integers in arr are distinct.
The integers in pieces are distinct (i.e., If we flatten pieces in a 1D array, all the integers in this array are distinct).

*/


# Algorithm

Encode with # to avoid 1,11 and 1,1,1 both contributing to 111. Then brute force way.

# Code

Java

Java

class Solution {
public boolean canFormArray(int[] arr, int[][] pieces) {
Map<Integer, Integer> map = new HashMap<Integer, Integer>();
int length = arr.length;
for (int i = 0; i < length; i++)
map.put(arr[i], i);
int[] flatPieces = new int[length];
for (int[] piece : pieces) {
int firstNum = piece;
int index = map.getOrDefault(firstNum, -1);
if (index < 0)
return false;
int curLength = piece.length;
if (index + curLength > length)
return false;
System.arraycopy(piece, 0, flatPieces, index, curLength);
}
return Arrays.equals(arr, flatPieces);
}
}