Check Array Formation Through Concatenation

Problem

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

Example 2:

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

Example 3:

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

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).

Solution (Java)

class Solution {
    public boolean canFormArray(int[] arr, int[][] pieces) {
        for (int[] piece : pieces) {
            int first = piece[0];
            int index = findIndex(arr, first);
            if (index == -1) {
                return false;
            }
            int i = 0;
            for (int j = index; i < piece.length && j < arr.length; i++, j++) {
                if (arr[j] != piece[i]) {
                    return false;
                }
            }
            if (i != piece.length) {
                return false;
            }
        }
        return true;
    }

    private int findIndex(int[] arr, int key) {
        for (int i = 0; i < arr.length; i++) {
            if (arr[i] == key) {
                return i;
            }
        }
        return -1;
    }
}

Explain:

nope.

Complexity:

Time complexity : O(n).
Space complexity : O(n).